| /* |
| * kernel/workqueue.c - generic async execution with shared worker pool |
| * |
| * Copyright (C) 2002 Ingo Molnar |
| * |
| * Derived from the taskqueue/keventd code by: |
| * David Woodhouse <dwmw2@infradead.org> |
| * Andrew Morton |
| * Kai Petzke <wpp@marie.physik.tu-berlin.de> |
| * Theodore Ts'o <tytso@mit.edu> |
| * |
| * Made to use alloc_percpu by Christoph Lameter. |
| * |
| * Copyright (C) 2010 SUSE Linux Products GmbH |
| * Copyright (C) 2010 Tejun Heo <tj@kernel.org> |
| * |
| * This is the generic async execution mechanism. Work items as are |
| * executed in process context. The worker pool is shared and |
| * automatically managed. There are two worker pools for each CPU (one for |
| * normal work items and the other for high priority ones) and some extra |
| * pools for workqueues which are not bound to any specific CPU - the |
| * number of these backing pools is dynamic. |
| * |
| * Please read Documentation/core-api/workqueue.rst for details. |
| */ |
| |
| #include <linux/export.h> |
| #include <linux/kernel.h> |
| #include <linux/sched.h> |
| #include <linux/init.h> |
| #include <linux/signal.h> |
| #include <linux/completion.h> |
| #include <linux/workqueue.h> |
| #include <linux/slab.h> |
| #include <linux/cpu.h> |
| #include <linux/notifier.h> |
| #include <linux/kthread.h> |
| #include <linux/hardirq.h> |
| #include <linux/mempolicy.h> |
| #include <linux/freezer.h> |
| #include <linux/kallsyms.h> |
| #include <linux/debug_locks.h> |
| #include <linux/lockdep.h> |
| #include <linux/idr.h> |
| #include <linux/jhash.h> |
| #include <linux/hashtable.h> |
| #include <linux/rculist.h> |
| #include <linux/nodemask.h> |
| #include <linux/moduleparam.h> |
| #include <linux/uaccess.h> |
| |
| #include "workqueue_internal.h" |
| |
| enum { |
| /* |
| * worker_pool flags |
| * |
| * A bound pool is either associated or disassociated with its CPU. |
| * While associated (!DISASSOCIATED), all workers are bound to the |
| * CPU and none has %WORKER_UNBOUND set and concurrency management |
| * is in effect. |
| * |
| * While DISASSOCIATED, the cpu may be offline and all workers have |
| * %WORKER_UNBOUND set and concurrency management disabled, and may |
| * be executing on any CPU. The pool behaves as an unbound one. |
| * |
| * Note that DISASSOCIATED should be flipped only while holding |
| * attach_mutex to avoid changing binding state while |
| * worker_attach_to_pool() is in progress. |
| */ |
| POOL_MANAGER_ACTIVE = 1 << 0, /* being managed */ |
| POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */ |
| |
| /* worker flags */ |
| WORKER_DIE = 1 << 1, /* die die die */ |
| WORKER_IDLE = 1 << 2, /* is idle */ |
| WORKER_PREP = 1 << 3, /* preparing to run works */ |
| WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */ |
| WORKER_UNBOUND = 1 << 7, /* worker is unbound */ |
| WORKER_REBOUND = 1 << 8, /* worker was rebound */ |
| |
| WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE | |
| WORKER_UNBOUND | WORKER_REBOUND, |
| |
| NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */ |
| |
| UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */ |
| BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */ |
| |
| MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */ |
| IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */ |
| |
| MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2, |
| /* call for help after 10ms |
| (min two ticks) */ |
| MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */ |
| CREATE_COOLDOWN = HZ, /* time to breath after fail */ |
| |
| /* |
| * Rescue workers are used only on emergencies and shared by |
| * all cpus. Give MIN_NICE. |
| */ |
| RESCUER_NICE_LEVEL = MIN_NICE, |
| HIGHPRI_NICE_LEVEL = MIN_NICE, |
| |
| WQ_NAME_LEN = 24, |
| }; |
| |
| /* |
| * Structure fields follow one of the following exclusion rules. |
| * |
| * I: Modifiable by initialization/destruction paths and read-only for |
| * everyone else. |
| * |
| * P: Preemption protected. Disabling preemption is enough and should |
| * only be modified and accessed from the local cpu. |
| * |
| * L: pool->lock protected. Access with pool->lock held. |
| * |
| * X: During normal operation, modification requires pool->lock and should |
| * be done only from local cpu. Either disabling preemption on local |
| * cpu or grabbing pool->lock is enough for read access. If |
| * POOL_DISASSOCIATED is set, it's identical to L. |
| * |
| * A: pool->attach_mutex protected. |
| * |
| * PL: wq_pool_mutex protected. |
| * |
| * PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads. |
| * |
| * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads. |
| * |
| * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or |
| * sched-RCU for reads. |
| * |
| * WQ: wq->mutex protected. |
| * |
| * WR: wq->mutex protected for writes. Sched-RCU protected for reads. |
| * |
| * MD: wq_mayday_lock protected. |
| */ |
| |
| /* struct worker is defined in workqueue_internal.h */ |
| |
| struct worker_pool { |
| spinlock_t lock; /* the pool lock */ |
| int cpu; /* I: the associated cpu */ |
| int node; /* I: the associated node ID */ |
| int id; /* I: pool ID */ |
| unsigned int flags; /* X: flags */ |
| |
| unsigned long watchdog_ts; /* L: watchdog timestamp */ |
| |
| struct list_head worklist; /* L: list of pending works */ |
| int nr_workers; /* L: total number of workers */ |
| |
| /* nr_idle includes the ones off idle_list for rebinding */ |
| int nr_idle; /* L: currently idle ones */ |
| |
| struct list_head idle_list; /* X: list of idle workers */ |
| struct timer_list idle_timer; /* L: worker idle timeout */ |
| struct timer_list mayday_timer; /* L: SOS timer for workers */ |
| |
| /* a workers is either on busy_hash or idle_list, or the manager */ |
| DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER); |
| /* L: hash of busy workers */ |
| |
| /* see manage_workers() for details on the two manager mutexes */ |
| struct worker *manager; /* L: purely informational */ |
| struct mutex attach_mutex; /* attach/detach exclusion */ |
| struct list_head workers; /* A: attached workers */ |
| struct completion *detach_completion; /* all workers detached */ |
| |
| struct ida worker_ida; /* worker IDs for task name */ |
| |
| struct workqueue_attrs *attrs; /* I: worker attributes */ |
| struct hlist_node hash_node; /* PL: unbound_pool_hash node */ |
| int refcnt; /* PL: refcnt for unbound pools */ |
| |
| /* |
| * The current concurrency level. As it's likely to be accessed |
| * from other CPUs during try_to_wake_up(), put it in a separate |
| * cacheline. |
| */ |
| atomic_t nr_running ____cacheline_aligned_in_smp; |
| |
| /* |
| * Destruction of pool is sched-RCU protected to allow dereferences |
| * from get_work_pool(). |
| */ |
| struct rcu_head rcu; |
| } ____cacheline_aligned_in_smp; |
| |
| /* |
| * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS |
| * of work_struct->data are used for flags and the remaining high bits |
| * point to the pwq; thus, pwqs need to be aligned at two's power of the |
| * number of flag bits. |
| */ |
| struct pool_workqueue { |
| struct worker_pool *pool; /* I: the associated pool */ |
| struct workqueue_struct *wq; /* I: the owning workqueue */ |
| int work_color; /* L: current color */ |
| int flush_color; /* L: flushing color */ |
| int refcnt; /* L: reference count */ |
| int nr_in_flight[WORK_NR_COLORS]; |
| /* L: nr of in_flight works */ |
| int nr_active; /* L: nr of active works */ |
| int max_active; /* L: max active works */ |
| struct list_head delayed_works; /* L: delayed works */ |
| struct list_head pwqs_node; /* WR: node on wq->pwqs */ |
| struct list_head mayday_node; /* MD: node on wq->maydays */ |
| |
| /* |
| * Release of unbound pwq is punted to system_wq. See put_pwq() |
| * and pwq_unbound_release_workfn() for details. pool_workqueue |
| * itself is also sched-RCU protected so that the first pwq can be |
| * determined without grabbing wq->mutex. |
| */ |
| struct work_struct unbound_release_work; |
| struct rcu_head rcu; |
| } __aligned(1 << WORK_STRUCT_FLAG_BITS); |
| |
| /* |
| * Structure used to wait for workqueue flush. |
| */ |
| struct wq_flusher { |
| struct list_head list; /* WQ: list of flushers */ |
| int flush_color; /* WQ: flush color waiting for */ |
| struct completion done; /* flush completion */ |
| }; |
| |
| struct wq_device; |
| |
| /* |
| * The externally visible workqueue. It relays the issued work items to |
| * the appropriate worker_pool through its pool_workqueues. |
| */ |
| struct workqueue_struct { |
| struct list_head pwqs; /* WR: all pwqs of this wq */ |
| struct list_head list; /* PR: list of all workqueues */ |
| |
| struct mutex mutex; /* protects this wq */ |
| int work_color; /* WQ: current work color */ |
| int flush_color; /* WQ: current flush color */ |
| atomic_t nr_pwqs_to_flush; /* flush in progress */ |
| struct wq_flusher *first_flusher; /* WQ: first flusher */ |
| struct list_head flusher_queue; /* WQ: flush waiters */ |
| struct list_head flusher_overflow; /* WQ: flush overflow list */ |
| |
| struct list_head maydays; /* MD: pwqs requesting rescue */ |
| struct worker *rescuer; /* I: rescue worker */ |
| |
| int nr_drainers; /* WQ: drain in progress */ |
| int saved_max_active; /* WQ: saved pwq max_active */ |
| |
| struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */ |
| struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */ |
| |
| #ifdef CONFIG_SYSFS |
| struct wq_device *wq_dev; /* I: for sysfs interface */ |
| #endif |
| #ifdef CONFIG_LOCKDEP |
| struct lockdep_map lockdep_map; |
| #endif |
| char name[WQ_NAME_LEN]; /* I: workqueue name */ |
| |
| /* |
| * Destruction of workqueue_struct is sched-RCU protected to allow |
| * walking the workqueues list without grabbing wq_pool_mutex. |
| * This is used to dump all workqueues from sysrq. |
| */ |
| struct rcu_head rcu; |
| |
| /* hot fields used during command issue, aligned to cacheline */ |
| unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */ |
| struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */ |
| struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */ |
| }; |
| |
| static struct kmem_cache *pwq_cache; |
| |
| static cpumask_var_t *wq_numa_possible_cpumask; |
| /* possible CPUs of each node */ |
| |
| static bool wq_disable_numa; |
| module_param_named(disable_numa, wq_disable_numa, bool, 0444); |
| |
| /* see the comment above the definition of WQ_POWER_EFFICIENT */ |
| static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT); |
| module_param_named(power_efficient, wq_power_efficient, bool, 0444); |
| |
| static bool wq_online; /* can kworkers be created yet? */ |
| |
| static bool wq_numa_enabled; /* unbound NUMA affinity enabled */ |
| |
| /* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */ |
| static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf; |
| |
| static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */ |
| static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */ |
| static DECLARE_WAIT_QUEUE_HEAD(wq_manager_wait); /* wait for manager to go away */ |
| |
| static LIST_HEAD(workqueues); /* PR: list of all workqueues */ |
| static bool workqueue_freezing; /* PL: have wqs started freezing? */ |
| |
| /* PL: allowable cpus for unbound wqs and work items */ |
| static cpumask_var_t wq_unbound_cpumask; |
| |
| /* CPU where unbound work was last round robin scheduled from this CPU */ |
| static DEFINE_PER_CPU(int, wq_rr_cpu_last); |
| |
| /* |
| * Local execution of unbound work items is no longer guaranteed. The |
| * following always forces round-robin CPU selection on unbound work items |
| * to uncover usages which depend on it. |
| */ |
| #ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU |
| static bool wq_debug_force_rr_cpu = true; |
| #else |
| static bool wq_debug_force_rr_cpu = false; |
| #endif |
| module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644); |
| |
| /* the per-cpu worker pools */ |
| static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools); |
| |
| static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */ |
| |
| /* PL: hash of all unbound pools keyed by pool->attrs */ |
| static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER); |
| |
| /* I: attributes used when instantiating standard unbound pools on demand */ |
| static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS]; |
| |
| /* I: attributes used when instantiating ordered pools on demand */ |
| static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS]; |
| |
| struct workqueue_struct *system_wq __read_mostly; |
| EXPORT_SYMBOL(system_wq); |
| struct workqueue_struct *system_highpri_wq __read_mostly; |
| EXPORT_SYMBOL_GPL(system_highpri_wq); |
| struct workqueue_struct *system_long_wq __read_mostly; |
| EXPORT_SYMBOL_GPL(system_long_wq); |
| struct workqueue_struct *system_unbound_wq __read_mostly; |
| EXPORT_SYMBOL_GPL(system_unbound_wq); |
| struct workqueue_struct *system_freezable_wq __read_mostly; |
| EXPORT_SYMBOL_GPL(system_freezable_wq); |
| struct workqueue_struct *system_power_efficient_wq __read_mostly; |
| EXPORT_SYMBOL_GPL(system_power_efficient_wq); |
| struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly; |
| EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq); |
| |
| static int worker_thread(void *__worker); |
| static void workqueue_sysfs_unregister(struct workqueue_struct *wq); |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/workqueue.h> |
| |
| #define assert_rcu_or_pool_mutex() \ |
| RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \ |
| !lockdep_is_held(&wq_pool_mutex), \ |
| "sched RCU or wq_pool_mutex should be held") |
| |
| #define assert_rcu_or_wq_mutex(wq) \ |
| RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \ |
| !lockdep_is_held(&wq->mutex), \ |
| "sched RCU or wq->mutex should be held") |
| |
| #define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \ |
| RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \ |
| !lockdep_is_held(&wq->mutex) && \ |
| !lockdep_is_held(&wq_pool_mutex), \ |
| "sched RCU, wq->mutex or wq_pool_mutex should be held") |
| |
| #define for_each_cpu_worker_pool(pool, cpu) \ |
| for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \ |
| (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \ |
| (pool)++) |
| |
| /** |
| * for_each_pool - iterate through all worker_pools in the system |
| * @pool: iteration cursor |
| * @pi: integer used for iteration |
| * |
| * This must be called either with wq_pool_mutex held or sched RCU read |
| * locked. If the pool needs to be used beyond the locking in effect, the |
| * caller is responsible for guaranteeing that the pool stays online. |
| * |
| * The if/else clause exists only for the lockdep assertion and can be |
| * ignored. |
| */ |
| #define for_each_pool(pool, pi) \ |
| idr_for_each_entry(&worker_pool_idr, pool, pi) \ |
| if (({ assert_rcu_or_pool_mutex(); false; })) { } \ |
| else |
| |
| /** |
| * for_each_pool_worker - iterate through all workers of a worker_pool |
| * @worker: iteration cursor |
| * @pool: worker_pool to iterate workers of |
| * |
| * This must be called with @pool->attach_mutex. |
| * |
| * The if/else clause exists only for the lockdep assertion and can be |
| * ignored. |
| */ |
| #define for_each_pool_worker(worker, pool) \ |
| list_for_each_entry((worker), &(pool)->workers, node) \ |
| if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \ |
| else |
| |
| /** |
| * for_each_pwq - iterate through all pool_workqueues of the specified workqueue |
| * @pwq: iteration cursor |
| * @wq: the target workqueue |
| * |
| * This must be called either with wq->mutex held or sched RCU read locked. |
| * If the pwq needs to be used beyond the locking in effect, the caller is |
| * responsible for guaranteeing that the pwq stays online. |
| * |
| * The if/else clause exists only for the lockdep assertion and can be |
| * ignored. |
| */ |
| #define for_each_pwq(pwq, wq) \ |
| list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \ |
| if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \ |
| else |
| |
| #ifdef CONFIG_DEBUG_OBJECTS_WORK |
| |
| static struct debug_obj_descr work_debug_descr; |
| |
| static void *work_debug_hint(void *addr) |
| { |
| return ((struct work_struct *) addr)->func; |
| } |
| |
| static bool work_is_static_object(void *addr) |
| { |
| struct work_struct *work = addr; |
| |
| return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work)); |
| } |
| |
| /* |
| * fixup_init is called when: |
| * - an active object is initialized |
| */ |
| static bool work_fixup_init(void *addr, enum debug_obj_state state) |
| { |
| struct work_struct *work = addr; |
| |
| switch (state) { |
| case ODEBUG_STATE_ACTIVE: |
| cancel_work_sync(work); |
| debug_object_init(work, &work_debug_descr); |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| /* |
| * fixup_free is called when: |
| * - an active object is freed |
| */ |
| static bool work_fixup_free(void *addr, enum debug_obj_state state) |
| { |
| struct work_struct *work = addr; |
| |
| switch (state) { |
| case ODEBUG_STATE_ACTIVE: |
| cancel_work_sync(work); |
| debug_object_free(work, &work_debug_descr); |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| static struct debug_obj_descr work_debug_descr = { |
| .name = "work_struct", |
| .debug_hint = work_debug_hint, |
| .is_static_object = work_is_static_object, |
| .fixup_init = work_fixup_init, |
| .fixup_free = work_fixup_free, |
| }; |
| |
| static inline void debug_work_activate(struct work_struct *work) |
| { |
| debug_object_activate(work, &work_debug_descr); |
| } |
| |
| static inline void debug_work_deactivate(struct work_struct *work) |
| { |
| debug_object_deactivate(work, &work_debug_descr); |
| } |
| |
| void __init_work(struct work_struct *work, int onstack) |
| { |
| if (onstack) |
| debug_object_init_on_stack(work, &work_debug_descr); |
| else |
| debug_object_init(work, &work_debug_descr); |
| } |
| EXPORT_SYMBOL_GPL(__init_work); |
| |
| void destroy_work_on_stack(struct work_struct *work) |
| { |
| debug_object_free(work, &work_debug_descr); |
| } |
| EXPORT_SYMBOL_GPL(destroy_work_on_stack); |
| |
| void destroy_delayed_work_on_stack(struct delayed_work *work) |
| { |
| destroy_timer_on_stack(&work->timer); |
| debug_object_free(&work->work, &work_debug_descr); |
| } |
| EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack); |
| |
| #else |
| static inline void debug_work_activate(struct work_struct *work) { } |
| static inline void debug_work_deactivate(struct work_struct *work) { } |
| #endif |
| |
| /** |
| * worker_pool_assign_id - allocate ID and assing it to @pool |
| * @pool: the pool pointer of interest |
| * |
| * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned |
| * successfully, -errno on failure. |
| */ |
| static int worker_pool_assign_id(struct worker_pool *pool) |
| { |
| int ret; |
| |
| lockdep_assert_held(&wq_pool_mutex); |
| |
| ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE, |
| GFP_KERNEL); |
| if (ret >= 0) { |
| pool->id = ret; |
| return 0; |
| } |
| return ret; |
| } |
| |
| /** |
| * unbound_pwq_by_node - return the unbound pool_workqueue for the given node |
| * @wq: the target workqueue |
| * @node: the node ID |
| * |
| * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU |
| * read locked. |
| * If the pwq needs to be used beyond the locking in effect, the caller is |
| * responsible for guaranteeing that the pwq stays online. |
| * |
| * Return: The unbound pool_workqueue for @node. |
| */ |
| static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq, |
| int node) |
| { |
| assert_rcu_or_wq_mutex_or_pool_mutex(wq); |
| |
| /* |
| * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a |
| * delayed item is pending. The plan is to keep CPU -> NODE |
| * mapping valid and stable across CPU on/offlines. Once that |
| * happens, this workaround can be removed. |
| */ |
| if (unlikely(node == NUMA_NO_NODE)) |
| return wq->dfl_pwq; |
| |
| return rcu_dereference_raw(wq->numa_pwq_tbl[node]); |
| } |
| |
| static unsigned int work_color_to_flags(int color) |
| { |
| return color << WORK_STRUCT_COLOR_SHIFT; |
| } |
| |
| static int get_work_color(struct work_struct *work) |
| { |
| return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) & |
| ((1 << WORK_STRUCT_COLOR_BITS) - 1); |
| } |
| |
| static int work_next_color(int color) |
| { |
| return (color + 1) % WORK_NR_COLORS; |
| } |
| |
| /* |
| * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data |
| * contain the pointer to the queued pwq. Once execution starts, the flag |
| * is cleared and the high bits contain OFFQ flags and pool ID. |
| * |
| * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling() |
| * and clear_work_data() can be used to set the pwq, pool or clear |
| * work->data. These functions should only be called while the work is |
| * owned - ie. while the PENDING bit is set. |
| * |
| * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq |
| * corresponding to a work. Pool is available once the work has been |
| * queued anywhere after initialization until it is sync canceled. pwq is |
| * available only while the work item is queued. |
| * |
| * %WORK_OFFQ_CANCELING is used to mark a work item which is being |
| * canceled. While being canceled, a work item may have its PENDING set |
| * but stay off timer and worklist for arbitrarily long and nobody should |
| * try to steal the PENDING bit. |
| */ |
| static inline void set_work_data(struct work_struct *work, unsigned long data, |
| unsigned long flags) |
| { |
| WARN_ON_ONCE(!work_pending(work)); |
| atomic_long_set(&work->data, data | flags | work_static(work)); |
| } |
| |
| static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq, |
| unsigned long extra_flags) |
| { |
| set_work_data(work, (unsigned long)pwq, |
| WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags); |
| } |
| |
| static void set_work_pool_and_keep_pending(struct work_struct *work, |
| int pool_id) |
| { |
| set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, |
| WORK_STRUCT_PENDING); |
| } |
| |
| static void set_work_pool_and_clear_pending(struct work_struct *work, |
| int pool_id) |
| { |
| /* |
| * The following wmb is paired with the implied mb in |
| * test_and_set_bit(PENDING) and ensures all updates to @work made |
| * here are visible to and precede any updates by the next PENDING |
| * owner. |
| */ |
| smp_wmb(); |
| set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0); |
| /* |
| * The following mb guarantees that previous clear of a PENDING bit |
| * will not be reordered with any speculative LOADS or STORES from |
| * work->current_func, which is executed afterwards. This possible |
| * reordering can lead to a missed execution on attempt to qeueue |
| * the same @work. E.g. consider this case: |
| * |
| * CPU#0 CPU#1 |
| * ---------------------------- -------------------------------- |
| * |
| * 1 STORE event_indicated |
| * 2 queue_work_on() { |
| * 3 test_and_set_bit(PENDING) |
| * 4 } set_..._and_clear_pending() { |
| * 5 set_work_data() # clear bit |
| * 6 smp_mb() |
| * 7 work->current_func() { |
| * 8 LOAD event_indicated |
| * } |
| * |
| * Without an explicit full barrier speculative LOAD on line 8 can |
| * be executed before CPU#0 does STORE on line 1. If that happens, |
| * CPU#0 observes the PENDING bit is still set and new execution of |
| * a @work is not queued in a hope, that CPU#1 will eventually |
| * finish the queued @work. Meanwhile CPU#1 does not see |
| * event_indicated is set, because speculative LOAD was executed |
| * before actual STORE. |
| */ |
| smp_mb(); |
| } |
| |
| static void clear_work_data(struct work_struct *work) |
| { |
| smp_wmb(); /* see set_work_pool_and_clear_pending() */ |
| set_work_data(work, WORK_STRUCT_NO_POOL, 0); |
| } |
| |
| static struct pool_workqueue *get_work_pwq(struct work_struct *work) |
| { |
| unsigned long data = atomic_long_read(&work->data); |
| |
| if (data & WORK_STRUCT_PWQ) |
| return (void *)(data & WORK_STRUCT_WQ_DATA_MASK); |
| else |
| return NULL; |
| } |
| |
| /** |
| * get_work_pool - return the worker_pool a given work was associated with |
| * @work: the work item of interest |
| * |
| * Pools are created and destroyed under wq_pool_mutex, and allows read |
| * access under sched-RCU read lock. As such, this function should be |
| * called under wq_pool_mutex or with preemption disabled. |
| * |
| * All fields of the returned pool are accessible as long as the above |
| * mentioned locking is in effect. If the returned pool needs to be used |
| * beyond the critical section, the caller is responsible for ensuring the |
| * returned pool is and stays online. |
| * |
| * Return: The worker_pool @work was last associated with. %NULL if none. |
| */ |
| static struct worker_pool *get_work_pool(struct work_struct *work) |
| { |
| unsigned long data = atomic_long_read(&work->data); |
| int pool_id; |
| |
| assert_rcu_or_pool_mutex(); |
| |
| if (data & WORK_STRUCT_PWQ) |
| return ((struct pool_workqueue *) |
| (data & WORK_STRUCT_WQ_DATA_MASK))->pool; |
| |
| pool_id = data >> WORK_OFFQ_POOL_SHIFT; |
| if (pool_id == WORK_OFFQ_POOL_NONE) |
| return NULL; |
| |
| return idr_find(&worker_pool_idr, pool_id); |
| } |
| |
| /** |
| * get_work_pool_id - return the worker pool ID a given work is associated with |
| * @work: the work item of interest |
| * |
| * Return: The worker_pool ID @work was last associated with. |
| * %WORK_OFFQ_POOL_NONE if none. |
| */ |
| static int get_work_pool_id(struct work_struct *work) |
| { |
| unsigned long data = atomic_long_read(&work->data); |
| |
| if (data & WORK_STRUCT_PWQ) |
| return ((struct pool_workqueue *) |
| (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id; |
| |
| return data >> WORK_OFFQ_POOL_SHIFT; |
| } |
| |
| static void mark_work_canceling(struct work_struct *work) |
| { |
| unsigned long pool_id = get_work_pool_id(work); |
| |
| pool_id <<= WORK_OFFQ_POOL_SHIFT; |
| set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING); |
| } |
| |
| static bool work_is_canceling(struct work_struct *work) |
| { |
| unsigned long data = atomic_long_read(&work->data); |
| |
| return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING); |
| } |
| |
| /* |
| * Policy functions. These define the policies on how the global worker |
| * pools are managed. Unless noted otherwise, these functions assume that |
| * they're being called with pool->lock held. |
| */ |
| |
| static bool __need_more_worker(struct worker_pool *pool) |
| { |
| return !atomic_read(&pool->nr_running); |
| } |
| |
| /* |
| * Need to wake up a worker? Called from anything but currently |
| * running workers. |
| * |
| * Note that, because unbound workers never contribute to nr_running, this |
| * function will always return %true for unbound pools as long as the |
| * worklist isn't empty. |
| */ |
| static bool need_more_worker(struct worker_pool *pool) |
| { |
| return !list_empty(&pool->worklist) && __need_more_worker(pool); |
| } |
| |
| /* Can I start working? Called from busy but !running workers. */ |
| static bool may_start_working(struct worker_pool *pool) |
| { |
| return pool->nr_idle; |
| } |
| |
| /* Do I need to keep working? Called from currently running workers. */ |
| static bool keep_working(struct worker_pool *pool) |
| { |
| return !list_empty(&pool->worklist) && |
| atomic_read(&pool->nr_running) <= 1; |
| } |
| |
| /* Do we need a new worker? Called from manager. */ |
| static bool need_to_create_worker(struct worker_pool *pool) |
| { |
| return need_more_worker(pool) && !may_start_working(pool); |
| } |
| |
| /* Do we have too many workers and should some go away? */ |
| static bool too_many_workers(struct worker_pool *pool) |
| { |
| bool managing = pool->flags & POOL_MANAGER_ACTIVE; |
| int nr_idle = pool->nr_idle + managing; /* manager is considered idle */ |
| int nr_busy = pool->nr_workers - nr_idle; |
| |
| return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy; |
| } |
| |
| /* |
| * Wake up functions. |
| */ |
| |
| /* Return the first idle worker. Safe with preemption disabled */ |
| static struct worker *first_idle_worker(struct worker_pool *pool) |
| { |
| if (unlikely(list_empty(&pool->idle_list))) |
| return NULL; |
| |
| return list_first_entry(&pool->idle_list, struct worker, entry); |
| } |
| |
| /** |
| * wake_up_worker - wake up an idle worker |
| * @pool: worker pool to wake worker from |
| * |
| * Wake up the first idle worker of @pool. |
| * |
| * CONTEXT: |
| * spin_lock_irq(pool->lock). |
| */ |
| static void wake_up_worker(struct worker_pool *pool) |
| { |
| struct worker *worker = first_idle_worker(pool); |
| |
| if (likely(worker)) |
| wake_up_process(worker->task); |
| } |
| |
| /** |
| * wq_worker_waking_up - a worker is waking up |
| * @task: task waking up |
| * @cpu: CPU @task is waking up to |
| * |
| * This function is called during try_to_wake_up() when a worker is |
| * being awoken. |
| * |
| * CONTEXT: |
| * spin_lock_irq(rq->lock) |
| */ |
| void wq_worker_waking_up(struct task_struct *task, int cpu) |
| { |
| struct worker *worker = kthread_data(task); |
| |
| if (!(worker->flags & WORKER_NOT_RUNNING)) { |
| WARN_ON_ONCE(worker->pool->cpu != cpu); |
| atomic_inc(&worker->pool->nr_running); |
| } |
| } |
| |
| /** |
| * wq_worker_sleeping - a worker is going to sleep |
| * @task: task going to sleep |
| * |
| * This function is called during schedule() when a busy worker is |
| * going to sleep. Worker on the same cpu can be woken up by |
| * returning pointer to its task. |
| * |
| * CONTEXT: |
| * spin_lock_irq(rq->lock) |
| * |
| * Return: |
| * Worker task on @cpu to wake up, %NULL if none. |
| */ |
| struct task_struct *wq_worker_sleeping(struct task_struct *task) |
| { |
| struct worker *worker = kthread_data(task), *to_wakeup = NULL; |
| struct worker_pool *pool; |
| |
| /* |
| * Rescuers, which may not have all the fields set up like normal |
| * workers, also reach here, let's not access anything before |
| * checking NOT_RUNNING. |
| */ |
| if (worker->flags & WORKER_NOT_RUNNING) |
| return NULL; |
| |
| pool = worker->pool; |
| |
| /* this can only happen on the local cpu */ |
| if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id())) |
| return NULL; |
| |
| /* |
| * The counterpart of the following dec_and_test, implied mb, |
| * worklist not empty test sequence is in insert_work(). |
| * Please read comment there. |
| * |
| * NOT_RUNNING is clear. This means that we're bound to and |
| * running on the local cpu w/ rq lock held and preemption |
| * disabled, which in turn means that none else could be |
| * manipulating idle_list, so dereferencing idle_list without pool |
| * lock is safe. |
| */ |
| if (atomic_dec_and_test(&pool->nr_running) && |
| !list_empty(&pool->worklist)) |
| to_wakeup = first_idle_worker(pool); |
| return to_wakeup ? to_wakeup->task : NULL; |
| } |
| |
| /** |
| * worker_set_flags - set worker flags and adjust nr_running accordingly |
| * @worker: self |
| * @flags: flags to set |
| * |
| * Set @flags in @worker->flags and adjust nr_running accordingly. |
| * |
| * CONTEXT: |
| * spin_lock_irq(pool->lock) |
| */ |
| static inline void worker_set_flags(struct worker *worker, unsigned int flags) |
| { |
| struct worker_pool *pool = worker->pool; |
| |
| WARN_ON_ONCE(worker->task != current); |
| |
| /* If transitioning into NOT_RUNNING, adjust nr_running. */ |
| if ((flags & WORKER_NOT_RUNNING) && |
| !(worker->flags & WORKER_NOT_RUNNING)) { |
| atomic_dec(&pool->nr_running); |
| } |
| |
| worker->flags |= flags; |
| } |
| |
| /** |
| * worker_clr_flags - clear worker flags and adjust nr_running accordingly |
| * @worker: self |
| * @flags: flags to clear |
| * |
| * Clear @flags in @worker->flags and adjust nr_running accordingly. |
| * |
| * CONTEXT: |
| * spin_lock_irq(pool->lock) |
| */ |
| static inline void worker_clr_flags(struct worker *worker, unsigned int flags) |
| { |
| struct worker_pool *pool = worker->pool; |
| unsigned int oflags = worker->flags; |
| |
| WARN_ON_ONCE(worker->task != current); |
| |
| worker->flags &= ~flags; |
| |
| /* |
| * If transitioning out of NOT_RUNNING, increment nr_running. Note |
| * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask |
| * of multiple flags, not a single flag. |
| */ |
| if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING)) |
| if (!(worker->flags & WORKER_NOT_RUNNING)) |
| atomic_inc(&pool->nr_running); |
| } |
| |
| /** |
| * find_worker_executing_work - find worker which is executing a work |
| * @pool: pool of interest |
| * @work: work to find worker for |
| * |
| * Find a worker which is executing @work on @pool by searching |
| * @pool->busy_hash which is keyed by the address of @work. For a worker |
| * to match, its current execution should match the address of @work and |
| * its work function. This is to avoid unwanted dependency between |
| * unrelated work executions through a work item being recycled while still |
| * being executed. |
| * |
| * This is a bit tricky. A work item may be freed once its execution |
| * starts and nothing prevents the freed area from being recycled for |
| * another work item. If the same work item address ends up being reused |
| * before the original execution finishes, workqueue will identify the |
| * recycled work item as currently executing and make it wait until the |
| * current execution finishes, introducing an unwanted dependency. |
| * |
| * This function checks the work item address and work function to avoid |
| * false positives. Note that this isn't complete as one may construct a |
| * work function which can introduce dependency onto itself through a |
| * recycled work item. Well, if somebody wants to shoot oneself in the |
| * foot that badly, there's only so much we can do, and if such deadlock |
| * actually occurs, it should be easy to locate the culprit work function. |
| * |
| * CONTEXT: |
| * spin_lock_irq(pool->lock). |
| * |
| * Return: |
| * Pointer to worker which is executing @work if found, %NULL |
| * otherwise. |
| */ |
| static struct worker *find_worker_executing_work(struct worker_pool *pool, |
| struct work_struct *work) |
| { |
| struct worker *worker; |
| |
| hash_for_each_possible(pool->busy_hash, worker, hentry, |
| (unsigned long)work) |
| if (worker->current_work == work && |
| worker->current_func == work->func) |
| return worker; |
| |
| return NULL; |
| } |
| |
| /** |
| * move_linked_works - move linked works to a list |
| * @work: start of series of works to be scheduled |
| * @head: target list to append @work to |
| * @nextp: out parameter for nested worklist walking |
| * |
| * Schedule linked works starting from @work to @head. Work series to |
| * be scheduled starts at @work and includes any consecutive work with |
| * WORK_STRUCT_LINKED set in its predecessor. |
| * |
| * If @nextp is not NULL, it's updated to point to the next work of |
| * the last scheduled work. This allows move_linked_works() to be |
| * nested inside outer list_for_each_entry_safe(). |
| * |
| * CONTEXT: |
| * spin_lock_irq(pool->lock). |
| */ |
| static void move_linked_works(struct work_struct *work, struct list_head *head, |
| struct work_struct **nextp) |
| { |
| struct work_struct *n; |
| |
| /* |
| * Linked worklist will always end before the end of the list, |
| * use NULL for list head. |
| */ |
| list_for_each_entry_safe_from(work, n, NULL, entry) { |
| list_move_tail(&work->entry, head); |
| if (!(*work_data_bits(work) & WORK_STRUCT_LINKED)) |
| break; |
| } |
| |
| /* |
| * If we're already inside safe list traversal and have moved |
| * multiple works to the scheduled queue, the next position |
| * needs to be updated. |
| */ |
| if (nextp) |
| *nextp = n; |
| } |
| |
| /** |
| * get_pwq - get an extra reference on the specified pool_workqueue |
| * @pwq: pool_workqueue to get |
| * |
| * Obtain an extra reference on @pwq. The caller should guarantee that |
| * @pwq has positive refcnt and be holding the matching pool->lock. |
| */ |
| static void get_pwq(struct pool_workqueue *pwq) |
| { |
| lockdep_assert_held(&pwq->pool->lock); |
| WARN_ON_ONCE(pwq->refcnt <= 0); |
| pwq->refcnt++; |
| } |
| |
| /** |
| * put_pwq - put a pool_workqueue reference |
| * @pwq: pool_workqueue to put |
| * |
| * Drop a reference of @pwq. If its refcnt reaches zero, schedule its |
| * destruction. The caller should be holding the matching pool->lock. |
| */ |
| static void put_pwq(struct pool_workqueue *pwq) |
| { |
| lockdep_assert_held(&pwq->pool->lock); |
| if (likely(--pwq->refcnt)) |
| return; |
| if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND))) |
| return; |
| /* |
| * @pwq can't be released under pool->lock, bounce to |
| * pwq_unbound_release_workfn(). This never recurses on the same |
| * pool->lock as this path is taken only for unbound workqueues and |
| * the release work item is scheduled on a per-cpu workqueue. To |
| * avoid lockdep warning, unbound pool->locks are given lockdep |
| * subclass of 1 in get_unbound_pool(). |
| */ |
| schedule_work(&pwq->unbound_release_work); |
| } |
| |
| /** |
| * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock |
| * @pwq: pool_workqueue to put (can be %NULL) |
| * |
| * put_pwq() with locking. This function also allows %NULL @pwq. |
| */ |
| static void put_pwq_unlocked(struct pool_workqueue *pwq) |
| { |
| if (pwq) { |
| /* |
| * As both pwqs and pools are sched-RCU protected, the |
| * following lock operations are safe. |
| */ |
| spin_lock_irq(&pwq->pool->lock); |
| put_pwq(pwq); |
| spin_unlock_irq(&pwq->pool->lock); |
| } |
| } |
| |
| static void pwq_activate_delayed_work(struct work_struct *work) |
| { |
| struct pool_workqueue *pwq = get_work_pwq(work); |
| |
| trace_workqueue_activate_work(work); |
| if (list_empty(&pwq->pool->worklist)) |
| pwq->pool->watchdog_ts = jiffies; |
| move_linked_works(work, &pwq->pool->worklist, NULL); |
| __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work)); |
| pwq->nr_active++; |
| } |
| |
| static void pwq_activate_first_delayed(struct pool_workqueue *pwq) |
| { |
| struct work_struct *work = list_first_entry(&pwq->delayed_works, |
| struct work_struct, entry); |
| |
| pwq_activate_delayed_work(work); |
| } |
| |
| /** |
| * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight |
| * @pwq: pwq of interest |
| * @color: color of work which left the queue |
| * |
| * A work either has completed or is removed from pending queue, |
| * decrement nr_in_flight of its pwq and handle workqueue flushing. |
| * |
| * CONTEXT: |
| * spin_lock_irq(pool->lock). |
| */ |
| static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color) |
| { |
| /* uncolored work items don't participate in flushing or nr_active */ |
| if (color == WORK_NO_COLOR) |
| goto out_put; |
| |
| pwq->nr_in_flight[color]--; |
| |
| pwq->nr_active--; |
| if (!list_empty(&pwq->delayed_works)) { |
| /* one down, submit a delayed one */ |
| if (pwq->nr_active < pwq->max_active) |
| pwq_activate_first_delayed(pwq); |
| } |
| |
| /* is flush in progress and are we at the flushing tip? */ |
| if (likely(pwq->flush_color != color)) |
| goto out_put; |
| |
| /* are there still in-flight works? */ |
| if (pwq->nr_in_flight[color]) |
| goto out_put; |
| |
| /* this pwq is done, clear flush_color */ |
| pwq->flush_color = -1; |
| |
| /* |
| * If this was the last pwq, wake up the first flusher. It |
| * will handle the rest. |
| */ |
| if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush)) |
| complete(&pwq->wq->first_flusher->done); |
| out_put: |
| put_pwq(pwq); |
| } |
| |
| /** |
| * try_to_grab_pending - steal work item from worklist and disable irq |
| * @work: work item to steal |
| * @is_dwork: @work is a delayed_work |
| * @flags: place to store irq state |
| * |
| * Try to grab PENDING bit of @work. This function can handle @work in any |
| * stable state - idle, on timer or on worklist. |
| * |
| * Return: |
| * 1 if @work was pending and we successfully stole PENDING |
| * 0 if @work was idle and we claimed PENDING |
| * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry |
| * -ENOENT if someone else is canceling @work, this state may persist |
| * for arbitrarily long |
| * |
| * Note: |
| * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting |
| * interrupted while holding PENDING and @work off queue, irq must be |
| * disabled on entry. This, combined with delayed_work->timer being |
| * irqsafe, ensures that we return -EAGAIN for finite short period of time. |
| * |
| * On successful return, >= 0, irq is disabled and the caller is |
| * responsible for releasing it using local_irq_restore(*@flags). |
| * |
| * This function is safe to call from any context including IRQ handler. |
| */ |
| static int try_to_grab_pending(struct work_struct *work, bool is_dwork, |
| unsigned long *flags) |
| { |
| struct worker_pool *pool; |
| struct pool_workqueue *pwq; |
| |
| local_irq_save(*flags); |
| |
| /* try to steal the timer if it exists */ |
| if (is_dwork) { |
| struct delayed_work *dwork = to_delayed_work(work); |
| |
| /* |
| * dwork->timer is irqsafe. If del_timer() fails, it's |
| * guaranteed that the timer is not queued anywhere and not |
| * running on the local CPU. |
| */ |
| if (likely(del_timer(&dwork->timer))) |
| return 1; |
| } |
| |
| /* try to claim PENDING the normal way */ |
| if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) |
| return 0; |
| |
| /* |
| * The queueing is in progress, or it is already queued. Try to |
| * steal it from ->worklist without clearing WORK_STRUCT_PENDING. |
| */ |
| pool = get_work_pool(work); |
| if (!pool) |
| goto fail; |
| |
| spin_lock(&pool->lock); |
| /* |
| * work->data is guaranteed to point to pwq only while the work |
| * item is queued on pwq->wq, and both updating work->data to point |
| * to pwq on queueing and to pool on dequeueing are done under |
| * pwq->pool->lock. This in turn guarantees that, if work->data |
| * points to pwq which is associated with a locked pool, the work |
| * item is currently queued on that pool. |
| */ |
| pwq = get_work_pwq(work); |
| if (pwq && pwq->pool == pool) { |
| debug_work_deactivate(work); |
| |
| /* |
| * A delayed work item cannot be grabbed directly because |
| * it might have linked NO_COLOR work items which, if left |
| * on the delayed_list, will confuse pwq->nr_active |
| * management later on and cause stall. Make sure the work |
| * item is activated before grabbing. |
| */ |
| if (*work_data_bits(work) & WORK_STRUCT_DELAYED) |
| pwq_activate_delayed_work(work); |
| |
| list_del_init(&work->entry); |
| pwq_dec_nr_in_flight(pwq, get_work_color(work)); |
| |
| /* work->data points to pwq iff queued, point to pool */ |
| set_work_pool_and_keep_pending(work, pool->id); |
| |
| spin_unlock(&pool->lock); |
| return 1; |
| } |
| spin_unlock(&pool->lock); |
| fail: |
| local_irq_restore(*flags); |
| if (work_is_canceling(work)) |
| return -ENOENT; |
| cpu_relax(); |
| return -EAGAIN; |
| } |
| |
| /** |
| * insert_work - insert a work into a pool |
| * @pwq: pwq @work belongs to |
| * @work: work to insert |
| * @head: insertion point |
| * @extra_flags: extra WORK_STRUCT_* flags to set |
| * |
| * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to |
| * work_struct flags. |
| * |
| * CONTEXT: |
| * spin_lock_irq(pool->lock). |
| */ |
| static void insert_work(struct pool_workqueue *pwq, struct work_struct *work, |
| struct list_head *head, unsigned int extra_flags) |
| { |
| struct worker_pool *pool = pwq->pool; |
| |
| /* we own @work, set data and link */ |
| set_work_pwq(work, pwq, extra_flags); |
| list_add_tail(&work->entry, head); |
| get_pwq(pwq); |
| |
| /* |
| * Ensure either wq_worker_sleeping() sees the above |
| * list_add_tail() or we see zero nr_running to avoid workers lying |
| * around lazily while there are works to be processed. |
| */ |
| smp_mb(); |
| |
| if (__need_more_worker(pool)) |
| wake_up_worker(pool); |
| } |
| |
| /* |
| * Test whether @work is being queued from another work executing on the |
| * same workqueue. |
| */ |
| static bool is_chained_work(struct workqueue_struct *wq) |
| { |
| struct worker *worker; |
| |
| worker = current_wq_worker(); |
| /* |
| * Return %true iff I'm a worker execuing a work item on @wq. If |
| * I'm @worker, it's safe to dereference it without locking. |
| */ |
| return worker && worker->current_pwq->wq == wq; |
| } |
| |
| /* |
| * When queueing an unbound work item to a wq, prefer local CPU if allowed |
| * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to |
| * avoid perturbing sensitive tasks. |
| */ |
| static int wq_select_unbound_cpu(int cpu) |
| { |
| static bool printed_dbg_warning; |
| int new_cpu; |
| |
| if (likely(!wq_debug_force_rr_cpu)) { |
| if (cpumask_test_cpu(cpu, wq_unbound_cpumask)) |
| return cpu; |
| } else if (!printed_dbg_warning) { |
| pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n"); |
| printed_dbg_warning = true; |
| } |
| |
| if (cpumask_empty(wq_unbound_cpumask)) |
| return cpu; |
| |
| new_cpu = __this_cpu_read(wq_rr_cpu_last); |
| new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask); |
| if (unlikely(new_cpu >= nr_cpu_ids)) { |
| new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask); |
| if (unlikely(new_cpu >= nr_cpu_ids)) |
| return cpu; |
| } |
| __this_cpu_write(wq_rr_cpu_last, new_cpu); |
| |
| return new_cpu; |
| } |
| |
| static void __queue_work(int cpu, struct workqueue_struct *wq, |
| struct work_struct *work) |
| { |
| struct pool_workqueue *pwq; |
| struct worker_pool *last_pool; |
| struct list_head *worklist; |
| unsigned int work_flags; |
| unsigned int req_cpu = cpu; |
| |
| /* |
| * While a work item is PENDING && off queue, a task trying to |
| * steal the PENDING will busy-loop waiting for it to either get |
| * queued or lose PENDING. Grabbing PENDING and queueing should |
| * happen with IRQ disabled. |
| */ |
| WARN_ON_ONCE(!irqs_disabled()); |
| |
| debug_work_activate(work); |
| |
| /* if draining, only works from the same workqueue are allowed */ |
| if (unlikely(wq->flags & __WQ_DRAINING) && |
| WARN_ON_ONCE(!is_chained_work(wq))) |
| return; |
| retry: |
| if (req_cpu == WORK_CPU_UNBOUND) |
| cpu = wq_select_unbound_cpu(raw_smp_processor_id()); |
| |
| /* pwq which will be used unless @work is executing elsewhere */ |
| if (!(wq->flags & WQ_UNBOUND)) |
| pwq = per_cpu_ptr(wq->cpu_pwqs, cpu); |
| else |
| pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu)); |
| |
| /* |
| * If @work was previously on a different pool, it might still be |
| * running there, in which case the work needs to be queued on that |
| * pool to guarantee non-reentrancy. |
| */ |
| last_pool = get_work_pool(work); |
| if (last_pool && last_pool != pwq->pool) { |
| struct worker *worker; |
| |
| spin_lock(&last_pool->lock); |
| |
| worker = find_worker_executing_work(last_pool, work); |
| |
| if (worker && worker->current_pwq->wq == wq) { |
| pwq = worker->current_pwq; |
| } else { |
| /* meh... not running there, queue here */ |
| spin_unlock(&last_pool->lock); |
| spin_lock(&pwq->pool->lock); |
| } |
| } else { |
| spin_lock(&pwq->pool->lock); |
| } |
| |
| /* |
| * pwq is determined and locked. For unbound pools, we could have |
| * raced with pwq release and it could already be dead. If its |
| * refcnt is zero, repeat pwq selection. Note that pwqs never die |
| * without another pwq replacing it in the numa_pwq_tbl or while |
| * work items are executing on it, so the retrying is guaranteed to |
| * make forward-progress. |
| */ |
| if (unlikely(!pwq->refcnt)) { |
| if (wq->flags & WQ_UNBOUND) { |
| spin_unlock(&pwq->pool->lock); |
| cpu_relax(); |
| goto retry; |
| } |
| /* oops */ |
| WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt", |
| wq->name, cpu); |
| } |
| |
| /* pwq determined, queue */ |
| trace_workqueue_queue_work(req_cpu, pwq, work); |
| |
| if (WARN_ON(!list_empty(&work->entry))) { |
| spin_unlock(&pwq->pool->lock); |
| return; |
| } |
| |
| pwq->nr_in_flight[pwq->work_color]++; |
| work_flags = work_color_to_flags(pwq->work_color); |
| |
| if (likely(pwq->nr_active < pwq->max_active)) { |
| trace_workqueue_activate_work(work); |
| pwq->nr_active++; |
| worklist = &pwq->pool->worklist; |
| if (list_empty(worklist)) |
| pwq->pool->watchdog_ts = jiffies; |
| } else { |
| work_flags |= WORK_STRUCT_DELAYED; |
| worklist = &pwq->delayed_works; |
| } |
| |
| insert_work(pwq, work, worklist, work_flags); |
| |
| spin_unlock(&pwq->pool->lock); |
| } |
| |
| /** |
| * queue_work_on - queue work on specific cpu |
| * @cpu: CPU number to execute work on |
| * @wq: workqueue to use |
| * @work: work to queue |
| * |
| * We queue the work to a specific CPU, the caller must ensure it |
| * can't go away. |
| * |
| * Return: %false if @work was already on a queue, %true otherwise. |
| */ |
| bool queue_work_on(int cpu, struct workqueue_struct *wq, |
| struct work_struct *work) |
| { |
| bool ret = false; |
| unsigned long flags; |
| |
| local_irq_save(flags); |
| |
| if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { |
| __queue_work(cpu, wq, work); |
| ret = true; |
| } |
| |
| local_irq_restore(flags); |
| return ret; |
| } |
| EXPORT_SYMBOL(queue_work_on); |
| |
| void delayed_work_timer_fn(unsigned long __data) |
| { |
| struct delayed_work *dwork = (struct delayed_work *)__data; |
| |
| /* should have been called from irqsafe timer with irq already off */ |
| __queue_work(dwork->cpu, dwork->wq, &dwork->work); |
| } |
| EXPORT_SYMBOL(delayed_work_timer_fn); |
| |
| static void __queue_delayed_work(int cpu, struct workqueue_struct *wq, |
| struct delayed_work *dwork, unsigned long delay) |
| { |
| struct timer_list *timer = &dwork->timer; |
| struct work_struct *work = &dwork->work; |
| |
| WARN_ON_ONCE(!wq); |
| WARN_ON_ONCE(timer->function != delayed_work_timer_fn || |
| timer->data != (unsigned long)dwork); |
| WARN_ON_ONCE(timer_pending(timer)); |
| WARN_ON_ONCE(!list_empty(&work->entry)); |
| |
| /* |
| * If @delay is 0, queue @dwork->work immediately. This is for |
| * both optimization and correctness. The earliest @timer can |
| * expire is on the closest next tick and delayed_work users depend |
| * on that there's no such delay when @delay is 0. |
| */ |
| if (!delay) { |
| __queue_work(cpu, wq, &dwork->work); |
| return; |
| } |
| |
| dwork->wq = wq; |
| dwork->cpu = cpu; |
| timer->expires = jiffies + delay; |
| |
| if (unlikely(cpu != WORK_CPU_UNBOUND)) |
| add_timer_on(timer, cpu); |
| else |
| add_timer(timer); |
| } |
| |
| /** |
| * queue_delayed_work_on - queue work on specific CPU after delay |
| * @cpu: CPU number to execute work on |
| * @wq: workqueue to use |
| * @dwork: work to queue |
| * @delay: number of jiffies to wait before queueing |
| * |
| * Return: %false if @work was already on a queue, %true otherwise. If |
| * @delay is zero and @dwork is idle, it will be scheduled for immediate |
| * execution. |
| */ |
| bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq, |
| struct delayed_work *dwork, unsigned long delay) |
| { |
| struct work_struct *work = &dwork->work; |
| bool ret = false; |
| unsigned long flags; |
| |
| /* read the comment in __queue_work() */ |
| local_irq_save(flags); |
| |
| if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { |
| __queue_delayed_work(cpu, wq, dwork, delay); |
| ret = true; |
| } |
| |
| local_irq_restore(flags); |
| return ret; |
| } |
| EXPORT_SYMBOL(queue_delayed_work_on); |
| |
| /** |
| * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU |
| * @cpu: CPU number to execute work on |
| * @wq: workqueue to use |
| * @dwork: work to queue |
| * @delay: number of jiffies to wait before queueing |
| * |
| * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise, |
| * modify @dwork's timer so that it expires after @delay. If @delay is |
| * zero, @work is guaranteed to be scheduled immediately regardless of its |
| * current state. |
| * |
| * Return: %false if @dwork was idle and queued, %true if @dwork was |
| * pending and its timer was modified. |
| * |
| * This function is safe to call from any context including IRQ handler. |
| * See try_to_grab_pending() for details. |
| */ |
| bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq, |
| struct delayed_work *dwork, unsigned long delay) |
| { |
| unsigned long flags; |
| int ret; |
| |
| do { |
| ret = try_to_grab_pending(&dwork->work, true, &flags); |
| } while (unlikely(ret == -EAGAIN)); |
| |
| if (likely(ret >= 0)) { |
| __queue_delayed_work(cpu, wq, dwork, delay); |
| local_irq_restore(flags); |
| } |
| |
| /* -ENOENT from try_to_grab_pending() becomes %true */ |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(mod_delayed_work_on); |
| |
| /** |
| * worker_enter_idle - enter idle state |
| * @worker: worker which is entering idle state |
| * |
| * @worker is entering idle state. Update stats and idle timer if |
| * necessary. |
| * |
| * LOCKING: |
| * spin_lock_irq(pool->lock). |
| */ |
| static void worker_enter_idle(struct worker *worker) |
| { |
| struct worker_pool *pool = worker->pool; |
| |
| if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) || |
| WARN_ON_ONCE(!list_empty(&worker->entry) && |
| (worker->hentry.next || worker->hentry.pprev))) |
| return; |
| |
| /* can't use worker_set_flags(), also called from create_worker() */ |
| worker->flags |= WORKER_IDLE; |
| pool->nr_idle++; |
| worker->last_active = jiffies; |
| |
| /* idle_list is LIFO */ |
| list_add(&worker->entry, &pool->idle_list); |
| |
| if (too_many_workers(pool) && !timer_pending(&pool->idle_timer)) |
| mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT); |
| |
| /* |
| * Sanity check nr_running. Because wq_unbind_fn() releases |
| * pool->lock between setting %WORKER_UNBOUND and zapping |
| * nr_running, the warning may trigger spuriously. Check iff |
| * unbind is not in progress. |
| */ |
| WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) && |
| pool->nr_workers == pool->nr_idle && |
| atomic_read(&pool->nr_running)); |
| } |
| |
| /** |
| * worker_leave_idle - leave idle state |
| * @worker: worker which is leaving idle state |
| * |
| * @worker is leaving idle state. Update stats. |
| * |
| * LOCKING: |
| * spin_lock_irq(pool->lock). |
| */ |
| static void worker_leave_idle(struct worker *worker) |
| { |
| struct worker_pool *pool = worker->pool; |
| |
| if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE))) |
| return; |
| worker_clr_flags(worker, WORKER_IDLE); |
| pool->nr_idle--; |
| list_del_init(&worker->entry); |
| } |
| |
| static struct worker *alloc_worker(int node) |
| { |
| struct worker *worker; |
| |
| worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node); |
| if (worker) { |
| INIT_LIST_HEAD(&worker->entry); |
| INIT_LIST_HEAD(&worker->scheduled); |
| INIT_LIST_HEAD(&worker->node); |
| /* on creation a worker is in !idle && prep state */ |
| worker->flags = WORKER_PREP; |
| } |
| return worker; |
| } |
| |
| /** |
| * worker_attach_to_pool() - attach a worker to a pool |
| * @worker: worker to be attached |
| * @pool: the target pool |
| * |
| * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and |
| * cpu-binding of @worker are kept coordinated with the pool across |
| * cpu-[un]hotplugs. |
| */ |
| static void worker_attach_to_pool(struct worker *worker, |
| struct worker_pool *pool) |
| { |
| mutex_lock(&pool->attach_mutex); |
| |
| /* |
| * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any |
| * online CPUs. It'll be re-applied when any of the CPUs come up. |
| */ |
| set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask); |
| |
| /* |
| * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains |
| * stable across this function. See the comments above the |
| * flag definition for details. |
| */ |
| if (pool->flags & POOL_DISASSOCIATED) |
| worker->flags |= WORKER_UNBOUND; |
| |
| list_add_tail(&worker->node, &pool->workers); |
| |
| mutex_unlock(&pool->attach_mutex); |
| } |
| |
| /** |
| * worker_detach_from_pool() - detach a worker from its pool |
| * @worker: worker which is attached to its pool |
| * @pool: the pool @worker is attached to |
| * |
| * Undo the attaching which had been done in worker_attach_to_pool(). The |
| * caller worker shouldn't access to the pool after detached except it has |
| * other reference to the pool. |
| */ |
| static void worker_detach_from_pool(struct worker *worker, |
| struct worker_pool *pool) |
| { |
| struct completion *detach_completion = NULL; |
| |
| mutex_lock(&pool->attach_mutex); |
| list_del(&worker->node); |
| if (list_empty(&pool->workers)) |
| detach_completion = pool->detach_completion; |
| mutex_unlock(&pool->attach_mutex); |
| |
| /* clear leftover flags without pool->lock after it is detached */ |
| worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND); |
| |
| if (detach_completion) |
| complete(detach_completion); |
| } |
| |
| /** |
| * create_worker - create a new workqueue worker |
| * @pool: pool the new worker will belong to |
| * |
| * Create and start a new worker which is attached to @pool. |
| * |
| * CONTEXT: |
| * Might sleep. Does GFP_KERNEL allocations. |
| * |
| * Return: |
| * Pointer to the newly created worker. |
| */ |
| static struct worker *create_worker(struct worker_pool *pool) |
| { |
| struct worker *worker = NULL; |
| int id = -1; |
| char id_buf[16]; |
| |
| /* ID is needed to determine kthread name */ |
| id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL); |
| if (id < 0) |
| goto fail; |
| |
| worker = alloc_worker(pool->node); |
| if (!worker) |
| goto fail; |
| |
| worker->pool = pool; |
| worker->id = id; |
| |
| if (pool->cpu >= 0) |
| snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id, |
| pool->attrs->nice < 0 ? "H" : ""); |
| else |
| snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id); |
| |
| worker->task = kthread_create_on_node(worker_thread, worker, pool->node, |
| "kworker/%s", id_buf); |
| if (IS_ERR(worker->task)) |
| goto fail; |
| |
| set_user_nice(worker->task, pool->attrs->nice); |
| kthread_bind_mask(worker->task, pool->attrs->cpumask); |
| |
| /* successful, attach the worker to the pool */ |
| worker_attach_to_pool(worker, pool); |
| |
| /* start the newly created worker */ |
| spin_lock_irq(&pool->lock); |
| worker->pool->nr_workers++; |
| worker_enter_idle(worker); |
| wake_up_process(worker->task); |
| spin_unlock_irq(&pool->lock); |
| |
| return worker; |
| |
| fail: |
| if (id >= 0) |
| ida_simple_remove(&pool->worker_ida, id); |
| kfree(worker); |
| return NULL; |
| } |
| |
| /** |
| * destroy_worker - destroy a workqueue worker |
| * @worker: worker to be destroyed |
| * |
| * Destroy @worker and adjust @pool stats accordingly. The worker should |
| * be idle. |
| * |
| * CONTEXT: |
| * spin_lock_irq(pool->lock). |
| */ |
| static void destroy_worker(struct worker *worker) |
| { |
| struct worker_pool *pool = worker->pool; |
| |
| lockdep_assert_held(&pool->lock); |
| |
| /* sanity check frenzy */ |
| if (WARN_ON(worker->current_work) || |
| WARN_ON(!list_empty(&worker->scheduled)) || |
| WARN_ON(!(worker->flags & WORKER_IDLE))) |
| return; |
| |
| pool->nr_workers--; |
| pool->nr_idle--; |
| |
| list_del_init(&worker->entry); |
| worker->flags |= WORKER_DIE; |
| wake_up_process(worker->task); |
| } |
| |
| static void idle_worker_timeout(unsigned long __pool) |
| { |
| struct worker_pool *pool = (void *)__pool; |
| |
| spin_lock_irq(&pool->lock); |
| |
| while (too_many_workers(pool)) { |
| struct worker *worker; |
| unsigned long expires; |
| |
| /* idle_list is kept in LIFO order, check the last one */ |
| worker = list_entry(pool->idle_list.prev, struct worker, entry); |
| expires = worker->last_active + IDLE_WORKER_TIMEOUT; |
| |
| if (time_before(jiffies, expires)) { |
| mod_timer(&pool->idle_timer, expires); |
| break; |
| } |
| |
| destroy_worker(worker); |
| } |
| |
| spin_unlock_irq(&pool->lock); |
| } |
| |
| static void send_mayday(struct work_struct *work) |
| { |
| struct pool_workqueue *pwq = get_work_pwq(work); |
| struct workqueue_struct *wq = pwq->wq; |
| |
| lockdep_assert_held(&wq_mayday_lock); |
| |
| if (!wq->rescuer) |
| return; |
| |
| /* mayday mayday mayday */ |
| if (list_empty(&pwq->mayday_node)) { |
| /* |
| * If @pwq is for an unbound wq, its base ref may be put at |
| * any time due to an attribute change. Pin @pwq until the |
| * rescuer is done with it. |
| */ |
| get_pwq(pwq); |
| list_add_tail(&pwq->mayday_node, &wq->maydays); |
| wake_up_process(wq->rescuer->task); |
| } |
| } |
| |
| static void pool_mayday_timeout(unsigned long __pool) |
| { |
| struct worker_pool *pool = (void *)__pool; |
| struct work_struct *work; |
| |
| spin_lock_irq(&pool->lock); |
| spin_lock(&wq_mayday_lock); /* for wq->maydays */ |
| |
| if (need_to_create_worker(pool)) { |
| /* |
| * We've been trying to create a new worker but |
| * haven't been successful. We might be hitting an |
| * allocation deadlock. Send distress signals to |
| * rescuers. |
| */ |
| list_for_each_entry(work, &pool->worklist, entry) |
| send_mayday(work); |
| } |
| |
| spin_unlock(&wq_mayday_lock); |
| spin_unlock_irq(&pool->lock); |
| |
| mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL); |
| } |
| |
| /** |
| * maybe_create_worker - create a new worker if necessary |
| * @pool: pool to create a new worker for |
| * |
| * Create a new worker for @pool if necessary. @pool is guaranteed to |
| * have at least one idle worker on return from this function. If |
| * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is |
| * sent to all rescuers with works scheduled on @pool to resolve |
| * possible allocation deadlock. |
| * |
| * On return, need_to_create_worker() is guaranteed to be %false and |
| * may_start_working() %true. |
| * |
| * LOCKING: |
| * spin_lock_irq(pool->lock) which may be released and regrabbed |
| * multiple times. Does GFP_KERNEL allocations. Called only from |
| * manager. |
| */ |
| static void maybe_create_worker(struct worker_pool *pool) |
| __releases(&pool->lock) |
| __acquires(&pool->lock) |
| { |
| restart: |
| spin_unlock_irq(&pool->lock); |
| |
| /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */ |
| mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT); |
| |
| while (true) { |
| if (create_worker(pool) || !need_to_create_worker(pool)) |
| break; |
| |
| schedule_timeout_interruptible(CREATE_COOLDOWN); |
| |
| if (!need_to_create_worker(pool)) |
| break; |
| } |
| |
| del_timer_sync(&pool->mayday_timer); |
| spin_lock_irq(&pool->lock); |
| /* |
| * This is necessary even after a new worker was just successfully |
| * created as @pool->lock was dropped and the new worker might have |
| * already become busy. |
| */ |
| if (need_to_create_worker(pool)) |
| goto restart; |
| } |
| |
| /** |
| * manage_workers - manage worker pool |
| * @worker: self |
| * |
| * Assume the manager role and manage the worker pool @worker belongs |
| * to. At any given time, there can be only zero or one manager per |
| * pool. The exclusion is handled automatically by this function. |
| * |
| * The caller can safely start processing works on false return. On |
| * true return, it's guaranteed that need_to_create_worker() is false |
| * and may_start_working() is true. |
| * |
| * CONTEXT: |
| * spin_lock_irq(pool->lock) which may be released and regrabbed |
| * multiple times. Does GFP_KERNEL allocations. |
| * |
| * Return: |
| * %false if the pool doesn't need management and the caller can safely |
| * start processing works, %true if management function was performed and |
| * the conditions that the caller verified before calling the function may |
| * no longer be true. |
| */ |
| static bool manage_workers(struct worker *worker) |
| { |
| struct worker_pool *pool = worker->pool; |
| |
| if (pool->flags & POOL_MANAGER_ACTIVE) |
| return false; |
| |
| pool->flags |= POOL_MANAGER_ACTIVE; |
| pool->manager = worker; |
| |
| maybe_create_worker(pool); |
| |
| pool->manager = NULL; |
| pool->flags &= ~POOL_MANAGER_ACTIVE; |
| wake_up(&wq_manager_wait); |
| return true; |
| } |
| |
| /** |
| * process_one_work - process single work |
| * @worker: self |
| * @work: work to process |
| * |
| * Process @work. This function contains all the logics necessary to |
| * process a single work including synchronization against and |
| * interaction with other workers on the same cpu, queueing and |
| * flushing. As long as context requirement is met, any worker can |
| * call this function to process a work. |
| * |
| * CONTEXT: |
| * spin_lock_irq(pool->lock) which is released and regrabbed. |
| */ |
| static void process_one_work(struct worker *worker, struct work_struct *work) |
| __releases(&pool->lock) |
| __acquires(&pool->lock) |
| { |
| struct pool_workqueue *pwq = get_work_pwq(work); |
| struct worker_pool *pool = worker->pool; |
| bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE; |
| int work_color; |
| struct worker *collision; |
| #ifdef CONFIG_LOCKDEP |
| /* |
| * It is permissible to free the struct work_struct from |
| * inside the function that is called from it, this we need to |
| * take into account for lockdep too. To avoid bogus "held |
| * lock freed" warnings as well as problems when looking into |
| * work->lockdep_map, make a copy and use that here. |
| */ |
| struct lockdep_map lockdep_map; |
| |
| lockdep_copy_map(&lockdep_map, &work->lockdep_map); |
| #endif |
| /* ensure we're on the correct CPU */ |
| WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) && |
| raw_smp_processor_id() != pool->cpu); |
| |
| /* |
| * A single work shouldn't be executed concurrently by |
| * multiple workers on a single cpu. Check whether anyone is |
| * already processing the work. If so, defer the work to the |
| * currently executing one. |
| */ |
| collision = find_worker_executing_work(pool, work); |
| if (unlikely(collision)) { |
| move_linked_works(work, &collision->scheduled, NULL); |
| return; |
| } |
| |
| /* claim and dequeue */ |
| debug_work_deactivate(work); |
| hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work); |
| worker->current_work = work; |
| worker->current_func = work->func; |
| worker->current_pwq = pwq; |
| work_color = get_work_color(work); |
| |
| list_del_init(&work->entry); |
| |
| /* |
| * CPU intensive works don't participate in concurrency management. |
| * They're the scheduler's responsibility. This takes @worker out |
| * of concurrency management and the next code block will chain |
| * execution of the pending work items. |
| */ |
| if (unlikely(cpu_intensive)) |
| worker_set_flags(worker, WORKER_CPU_INTENSIVE); |
| |
| /* |
| * Wake up another worker if necessary. The condition is always |
| * false for normal per-cpu workers since nr_running would always |
| * be >= 1 at this point. This is used to chain execution of the |
| * pending work items for WORKER_NOT_RUNNING workers such as the |
| * UNBOUND and CPU_INTENSIVE ones. |
| */ |
| if (need_more_worker(pool)) |
| wake_up_worker(pool); |
| |
| /* |
| * Record the last pool and clear PENDING which should be the last |
| * update to @work. Also, do this inside @pool->lock so that |
| * PENDING and queued state changes happen together while IRQ is |
| * disabled. |
| */ |
| set_work_pool_and_clear_pending(work, pool->id); |
| |
| spin_unlock_irq(&pool->lock); |
| |
| lock_map_acquire(&pwq->wq->lockdep_map); |
| lock_map_acquire(&lockdep_map); |
| /* |
| * Strictly speaking we should mark the invariant state without holding |
| * any locks, that is, before these two lock_map_acquire()'s. |
| * |
| * However, that would result in: |
| * |
| * A(W1) |
| * WFC(C) |
| * A(W1) |
| * C(C) |
| * |
| * Which would create W1->C->W1 dependencies, even though there is no |
| * actual deadlock possible. There are two solutions, using a |
| * read-recursive acquire on the work(queue) 'locks', but this will then |
| * hit the lockdep limitation on recursive locks, or simply discard |
| * these locks. |
| * |
| * AFAICT there is no possible deadlock scenario between the |
| * flush_work() and complete() primitives (except for single-threaded |
| * workqueues), so hiding them isn't a problem. |
| */ |
| lockdep_invariant_state(true); |
| trace_workqueue_execute_start(work); |
| worker->current_func(work); |
| /* |
| * While we must be careful to not use "work" after this, the trace |
| * point will only record its address. |
| */ |
| trace_workqueue_execute_end(work); |
| lock_map_release(&lockdep_map); |
| lock_map_release(&pwq->wq->lockdep_map); |
| |
| if (unlikely(in_atomic() || lockdep_depth(current) > 0)) { |
| pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n" |
| " last function: %pf\n", |
| current->comm, preempt_count(), task_pid_nr(current), |
| worker->current_func); |
| debug_show_held_locks(current); |
| dump_stack(); |
| } |
| |
| /* |
| * The following prevents a kworker from hogging CPU on !PREEMPT |
| * kernels, where a requeueing work item waiting for something to |
| * happen could deadlock with stop_machine as such work item could |
| * indefinitely requeue itself while all other CPUs are trapped in |
| * stop_machine. At the same time, report a quiescent RCU state so |
| * the same condition doesn't freeze RCU. |
| */ |
| cond_resched_rcu_qs(); |
| |
| spin_lock_irq(&pool->lock); |
| |
| /* clear cpu intensive status */ |
| if (unlikely(cpu_intensive)) |
| worker_clr_flags(worker, WORKER_CPU_INTENSIVE); |
| |
| /* we're done with it, release */ |
| hash_del(&worker->hentry); |
| worker->current_work = NULL; |
| worker->current_func = NULL; |
| worker->current_pwq = NULL; |
| worker->desc_valid = false; |
| pwq_dec_nr_in_flight(pwq, work_color); |
| } |
| |
| /** |
| * process_scheduled_works - process scheduled works |
| * @worker: self |
| * |
| * Process all scheduled works. Please note that the scheduled list |
| * may change while processing a work, so this function repeatedly |
| * fetches a work from the top and executes it. |
| * |
| * CONTEXT: |
| * spin_lock_irq(pool->lock) which may be released and regrabbed |
| * multiple times. |
| */ |
| static void process_scheduled_works(struct worker *worker) |
| { |
| while (!list_empty(&worker->scheduled)) { |
| struct work_struct *work = list_first_entry(&worker->scheduled, |
| struct work_struct, entry); |
| process_one_work(worker, work); |
| } |
| } |
| |
| /** |
| * worker_thread - the worker thread function |
| * @__worker: self |
| * |
| * The worker thread function. All workers belong to a worker_pool - |
| * either a per-cpu one or dynamic unbound one. These workers process all |
| * work items regardless of their specific target workqueue. The only |
| * exception is work items which belong to workqueues with a rescuer which |
| * will be explained in rescuer_thread(). |
| * |
| * Return: 0 |
| */ |
| static int worker_thread(void *__worker) |
| { |
| struct worker *worker = __worker; |
| struct worker_pool *pool = worker->pool; |
| |
| /* tell the scheduler that this is a workqueue worker */ |
| worker->task->flags |= PF_WQ_WORKER; |
| woke_up: |
| spin_lock_irq(&pool->lock); |
| |
| /* am I supposed to die? */ |
| if (unlikely(worker->flags & WORKER_DIE)) { |
| spin_unlock_irq(&pool->lock); |
| WARN_ON_ONCE(!list_empty(&worker->entry)); |
| worker->task->flags &= ~PF_WQ_WORKER; |
| |
| set_task_comm(worker->task, "kworker/dying"); |
| ida_simple_remove(&pool->worker_ida, worker->id); |
| worker_detach_from_pool(worker, pool); |
| kfree(worker); |
| return 0; |
| } |
| |
| worker_leave_idle(worker); |
| recheck: |
| /* no more worker necessary? */ |
| if (!need_more_worker(pool)) |
| goto sleep; |
| |
| /* do we need to manage? */ |
| if (unlikely(!may_start_working(pool)) && manage_workers(worker)) |
| goto recheck; |
| |
| /* |
| * ->scheduled list can only be filled while a worker is |
| * preparing to process a work or actually processing it. |
| * Make sure nobody diddled with it while I was sleeping. |
| */ |
| WARN_ON_ONCE(!list_empty(&worker->scheduled)); |
| |
| /* |
| * Finish PREP stage. We're guaranteed to have at least one idle |
| * worker or that someone else has already assumed the manager |
| * role. This is where @worker starts participating in concurrency |
| * management if applicable and concurrency management is restored |
| * after being rebound. See rebind_workers() for details. |
| */ |
| worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND); |
| |
| do { |
| struct work_struct *work = |
| list_first_entry(&pool->worklist, |
| struct work_struct, entry); |
| |
| pool->watchdog_ts = jiffies; |
| |
| if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) { |
| /* optimization path, not strictly necessary */ |
| process_one_work(worker, work); |
| if (unlikely(!list_empty(&worker->scheduled))) |
| process_scheduled_works(worker); |
| } else { |
| move_linked_works(work, &worker->scheduled, NULL); |
| process_scheduled_works(worker); |
| } |
| } while (keep_working(pool)); |
| |
| worker_set_flags(worker, WORKER_PREP); |
| sleep: |
| /* |
| * pool->lock is held and there's no work to process and no need to |
| * manage, sleep. Workers are woken up only while holding |
| * pool->lock or from local cpu, so setting the current state |
| * before releasing pool->lock is enough to prevent losing any |
| * event. |
| */ |
| worker_enter_idle(worker); |
| __set_current_state(TASK_IDLE); |
| spin_unlock_irq(&pool->lock); |
| schedule(); |
| goto woke_up; |
| } |
| |
| /** |
| * rescuer_thread - the rescuer thread function |
| * @__rescuer: self |
| * |
| * Workqueue rescuer thread function. There's one rescuer for each |
| * workqueue which has WQ_MEM_RECLAIM set. |
| * |
| * Regular work processing on a pool may block trying to create a new |
| * worker which uses GFP_KERNEL allocation which has slight chance of |
| * developing into deadlock if some works currently on the same queue |
| * need to be processed to satisfy the GFP_KERNEL allocation. This is |
| * the problem rescuer solves. |
| * |
| * When such condition is possible, the pool summons rescuers of all |
| * workqueues which have works queued on the pool and let them process |
| * those works so that forward progress can be guaranteed. |
| * |
| * This should happen rarely. |
| * |
| * Return: 0 |
| */ |
| static int rescuer_thread(void *__rescuer) |
| { |
| struct worker *rescuer = __rescuer; |
| struct workqueue_struct *wq = rescuer->rescue_wq; |
| struct list_head *scheduled = &rescuer->scheduled; |
| bool should_stop; |
| |
| set_user_nice(current, RESCUER_NICE_LEVEL); |
| |
| /* |
| * Mark rescuer as worker too. As WORKER_PREP is never cleared, it |
| * doesn't participate in concurrency management. |
| */ |
| rescuer->task->flags |= PF_WQ_WORKER; |
| repeat: |
| set_current_state(TASK_IDLE); |
| |
| /* |
| * By the time the rescuer is requested to stop, the workqueue |
| * shouldn't have any work pending, but @wq->maydays may still have |
| * pwq(s) queued. This can happen by non-rescuer workers consuming |
| * all the work items before the rescuer got to them. Go through |
| * @wq->maydays processing before acting on should_stop so that the |
| * list is always empty on exit. |
| */ |
| should_stop = kthread_should_stop(); |
| |
| /* see whether any pwq is asking for help */ |
| spin_lock_irq(&wq_mayday_lock); |
| |
| while (!list_empty(&wq->maydays)) { |
| struct pool_workqueue *pwq = list_first_entry(&wq->maydays, |
| struct pool_workqueue, mayday_node); |
| struct worker_pool *pool = pwq->pool; |
| struct work_struct *work, *n; |
| bool first = true; |
| |
| __set_current_state(TASK_RUNNING); |
| list_del_init(&pwq->mayday_node); |
| |
| spin_unlock_irq(&wq_mayday_lock); |
| |
| worker_attach_to_pool(rescuer, pool); |
| |
| spin_lock_irq(&pool->lock); |
| rescuer->pool = pool; |
| |
| /* |
| * Slurp in all works issued via this workqueue and |
| * process'em. |
| */ |
| WARN_ON_ONCE(!list_empty(scheduled)); |
| list_for_each_entry_safe(work, n, &pool->worklist, entry) { |
| if (get_work_pwq(work) == pwq) { |
| if (first) |
| pool->watchdog_ts = jiffies; |
| move_linked_works(work, scheduled, &n); |
| } |
| first = false; |
| } |
| |
| if (!list_empty(scheduled)) { |
| process_scheduled_works(rescuer); |
| |
| /* |
| * The above execution of rescued work items could |
| * have created more to rescue through |
| * pwq_activate_first_delayed() or chained |
| * queueing. Let's put @pwq back on mayday list so |
| * that such back-to-back work items, which may be |
| * being used to relieve memory pressure, don't |
| * incur MAYDAY_INTERVAL delay inbetween. |
| */ |
| if (need_to_create_worker(pool)) { |
| spin_lock(&wq_mayday_lock); |
| get_pwq(pwq); |
| list_move_tail(&pwq->mayday_node, &wq->maydays); |
| spin_unlock(&wq_mayday_lock); |
| } |
| } |
| |
| /* |
| * Put the reference grabbed by send_mayday(). @pool won't |
| * go away while we're still attached to it. |
| */ |
| put_pwq(pwq); |
| |
| /* |
| * Leave this pool. If need_more_worker() is %true, notify a |
| * regular worker; otherwise, we end up with 0 concurrency |
| * and stalling the execution. |
| */ |
| if (need_more_worker(pool)) |
| wake_up_worker(pool); |
| |
| rescuer->pool = NULL; |
| spin_unlock_irq(&pool->lock); |
| |
| worker_detach_from_pool(rescuer, pool); |
| |
| spin_lock_irq(&wq_mayday_lock); |
| } |
| |
| spin_unlock_irq(&wq_mayday_lock); |
| |
| if (should_stop) { |
| __set_current_state(TASK_RUNNING); |
| rescuer->task->flags &= ~PF_WQ_WORKER; |
| return 0; |
| } |
| |
| /* rescuers should never participate in concurrency management */ |
| WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING)); |
| schedule(); |
| goto repeat; |
| } |
| |
| /** |
| * check_flush_dependency - check for flush dependency sanity |
| * @target_wq: workqueue being flushed |
| * @target_work: work item being flushed (NULL for workqueue flushes) |
| * |
| * %current is trying to flush the whole @target_wq or @target_work on it. |
| * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not |
| * reclaiming memory or running on a workqueue which doesn't have |
| * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to |
| * a deadlock. |
| */ |
| static void check_flush_dependency(struct workqueue_struct *target_wq, |
| struct work_struct *target_work) |
| { |
| work_func_t target_func = target_work ? target_work->func : NULL; |
| struct worker *worker; |
| |
| if (target_wq->flags & WQ_MEM_RECLAIM) |
| return; |
| |
| worker = current_wq_worker(); |
| |
| WARN_ONCE(current->flags & PF_MEMALLOC, |
| "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf", |
| current->pid, current->comm, target_wq->name, target_func); |
| WARN_ONCE(worker && ((worker->current_pwq->wq->flags & |
| (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM), |
| "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf", |
| worker->current_pwq->wq->name, worker->current_func, |
| target_wq->name, target_func); |
| } |
| |
| struct wq_barrier { |
| struct work_struct work; |
| struct completion done; |
| struct task_struct *task; /* purely informational */ |
| }; |
| |
| static void wq_barrier_func(struct work_struct *work) |
| { |
| struct wq_barrier *barr = container_of(work, struct wq_barrier, work); |
| complete(&barr->done); |
| } |
| |
| /** |
| * insert_wq_barrier - insert a barrier work |
| * @pwq: pwq to insert barrier into |
| * @barr: wq_barrier to insert |
| * @target: target work to attach @barr to |
| * @worker: worker currently executing @target, NULL if @target is not executing |
| * |
| * @barr is linked to @target such that @barr is completed only after |
| * @target finishes execution. Please note that the ordering |
| * guarantee is observed only with respect to @target and on the local |
| * cpu. |
| * |
| * Currently, a queued barrier can't be canceled. This is because |
| * try_to_grab_pending() can't determine whether the work to be |
| * grabbed is at the head of the queue and thus can't clear LINKED |
| * flag of the previous work while there must be a valid next work |
| * after a work with LINKED flag set. |
| * |
| * Note that when @worker is non-NULL, @target may be modified |
| * underneath us, so we can't reliably determine pwq from @target. |
| * |
| * CONTEXT: |
| * spin_lock_irq(pool->lock). |
| */ |
| static void insert_wq_barrier(struct pool_workqueue *pwq, |
| struct wq_barrier *barr, |
| struct work_struct *target, struct worker *worker) |
| { |
| struct list_head *head; |
| unsigned int linked = 0; |
| |
| /* |
| * debugobject calls are safe here even with pool->lock locked |
| * as we know for sure that this will not trigger any of the |
| * checks and call back into the fixup functions where we |
| * might deadlock. |
| */ |
| INIT_WORK_ONSTACK(&barr->work, wq_barrier_func); |
| __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work)); |
| |
| /* |
| * Explicitly init the crosslock for wq_barrier::done, make its lock |
| * key a subkey of the corresponding work. As a result we won't |
| * build a dependency between wq_barrier::done and unrelated work. |
| */ |
| lockdep_init_map_crosslock((struct lockdep_map *)&barr->done.map, |
| "(complete)wq_barr::done", |
| target->lockdep_map.key, 1); |
| __init_completion(&barr->done); |
| barr->task = current; |
| |
| /* |
| * If @target is currently being executed, schedule the |
| * barrier to the worker; otherwise, put it after @target. |
| */ |
| if (worker) |
| head = worker->scheduled.next; |
| else { |
| unsigned long *bits = work_data_bits(target); |
| |
| head = target->entry.next; |
| /* there can already be other linked works, inherit and set */ |
| linked = *bits & WORK_STRUCT_LINKED; |
| __set_bit(WORK_STRUCT_LINKED_BIT, bits); |
| } |
| |
| debug_work_activate(&barr->work); |
| insert_work(pwq, &barr->work, head, |
| work_color_to_flags(WORK_NO_COLOR) | linked); |
| } |
| |
| /** |
| * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing |
| * @wq: workqueue being flushed |
| * @flush_color: new flush color, < 0 for no-op |
| * @work_color: new work color, < 0 for no-op |
| * |
| * Prepare pwqs for workqueue flushing. |
| * |
| * If @flush_color is non-negative, flush_color on all pwqs should be |
| * -1. If no pwq has in-flight commands at the specified color, all |
| * pwq->flush_color's stay at -1 and %false is returned. If any pwq |
| * has in flight commands, its pwq->flush_color is set to |
| * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq |
| * wakeup logic is armed and %true is returned. |
| * |
| * The caller should have initialized @wq->first_flusher prior to |
| * calling this function with non-negative @flush_color. If |
| * @flush_color is negative, no flush color update is done and %false |
| * is returned. |
| * |
| * If @work_color is non-negative, all pwqs should have the same |
| * work_color which is previous to @work_color and all will be |
| * advanced to @work_color. |
| * |
| * CONTEXT: |
| * mutex_lock(wq->mutex). |
| * |
| * Return: |
| * %true if @flush_color >= 0 and there's something to flush. %false |
| * otherwise. |
| */ |
| static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq, |
| int flush_color, int work_color) |
| { |
| bool wait = false; |
| struct pool_workqueue *pwq; |
| |
| if (flush_color >= 0) { |
| WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush)); |
| atomic_set(&wq->nr_pwqs_to_flush, 1); |
| } |
| |
| for_each_pwq(pwq, wq) { |
| struct worker_pool *pool = pwq->pool; |
| |
| spin_lock_irq(&pool->lock); |
| |
| if (flush_color >= 0) { |
| WARN_ON_ONCE(pwq->flush_color != -1); |
| |
| if (pwq->nr_in_flight[flush_color]) { |
| pwq->flush_color = flush_color; |
| atomic_inc(&wq->nr_pwqs_to_flush); |
| wait = true; |
| } |
| } |
| |
| if (work_color >= 0) { |
| WARN_ON_ONCE(work_color != work_next_color(pwq->work_color)); |
| pwq->work_color = work_color; |
| } |
| |
| spin_unlock_irq(&pool->lock); |
| } |
| |
| if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush)) |
| complete(&wq->first_flusher->done); |
| |
| return wait; |
| } |
| |
| /** |
| * flush_workqueue - ensure that any scheduled work has run to completion. |
| * @wq: workqueue to flush |
| * |
| * This function sleeps until all work items which were queued on entry |
| * have finished execution, but it is not livelocked by new incoming ones. |
| */ |
| void flush_workqueue(struct workqueue_struct *wq) |
| { |
| struct wq_flusher this_flusher = { |
| .list = LIST_HEAD_INIT(this_flusher.list), |
| .flush_color = -1, |
| .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done), |
| }; |
| int next_color; |
| |
| if (WARN_ON(!wq_online)) |
| return; |
| |
| lock_map_acquire(&wq->lockdep_map); |
| lock_map_release(&wq->lockdep_map); |
| |
| mutex_lock(&wq->mutex); |
| |
| /* |
| * Start-to-wait phase |
| */ |
| next_color = work_next_color(wq->work_color); |
| |
| if (next_color != wq->flush_color) { |
| /* |
| * Color space is not full. The current work_color |
| * becomes our flush_color and work_color is advanced |
| * by one. |
| */ |
| WARN_ON_ONCE(!list_empty(&wq->flusher_overflow)); |
| this_flusher.flush_color = wq->work_color; |
| wq->work_color = next_color; |
| |
| if (!wq->first_flusher) { |
| /* no flush in progress, become the first flusher */ |
| WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color); |
| |
| wq->first_flusher = &this_flusher; |
| |
| if (!flush_workqueue_prep_pwqs(wq, wq->flush_color, |
| wq->work_color)) { |
| /* nothing to flush, done */ |
| wq->flush_color = next_color; |
| wq->first_flusher = NULL; |
| goto out_unlock; |
| } |
| } else { |
| /* wait in queue */ |
| WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color); |
| list_add_tail(&this_flusher.list, &wq->flusher_queue); |
| flush_workqueue_prep_pwqs(wq, -1, wq->work_color); |
| } |
| } else { |
| /* |
| * Oops, color space is full, wait on overflow queue. |
| * The next flush completion will assign us |
| * flush_color and transfer to flusher_queue. |
| */ |
| list_add_tail(&this_flusher.list, &wq->flusher_overflow); |
| } |
| |
| check_flush_dependency(wq, NULL); |
| |
| mutex_unlock(&wq->mutex); |
| |
| wait_for_completion(&this_flusher.done); |
| |
| /* |
| * Wake-up-and-cascade phase |
| * |
| * First flushers are responsible for cascading flushes and |
| * handling overflow. Non-first flushers can simply return. |
| */ |
| if (wq->first_flusher != &this_flusher) |
| return; |
| |
| mutex_lock(&wq->mutex); |
| |
| /* we might have raced, check again with mutex held */ |
| if (wq->first_flusher != &this_flusher) |
| goto out_unlock; |
| |
| wq->first_flusher = NULL; |
| |
| WARN_ON_ONCE(!list_empty(&this_flusher.list)); |
| WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color); |
| |
| while (true) { |
| struct wq_flusher *next, *tmp; |
| |
| /* complete all the flushers sharing the current flush color */ |
| list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) { |
| if (next->flush_color != wq->flush_color) |
| break; |
| list_del_init(&next->list); |
| complete(&next->done); |
| } |
| |
| WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) && |
| wq->flush_color != work_next_color(wq->work_color)); |
| |
| /* this flush_color is finished, advance by one */ |
| wq->flush_color = work_next_color(wq->flush_color); |
| |
| /* one color has been freed, handle overflow queue */ |
| if (!list_empty(&wq->flusher_overflow)) { |
| /* |
| * Assign the same color to all overflowed |
| * flushers, advance work_color and append to |
| * flusher_queue. This is the start-to-wait |
| * phase for these overflowed flushers. |
| */ |
| list_for_each_entry(tmp, &wq->flusher_overflow, list) |
| tmp->flush_color = wq->work_color; |
| |
| wq->work_color = work_next_color(wq->work_color); |
| |
| list_splice_tail_init(&wq->flusher_overflow, |
| &wq->flusher_queue); |
| flush_workqueue_prep_pwqs(wq, -1, wq->work_color); |
| } |
| |
| if (list_empty(&wq->flusher_queue)) { |
| WARN_ON_ONCE(wq->flush_color != wq->work_color); |
| break; |
| } |
| |
| /* |
| * Need to flush more colors. Make the next flusher |
| * the new first flusher and arm pwqs. |
| */ |
| WARN_ON_ONCE(wq->flush_color == wq->work_color); |
| WARN_ON_ONCE(wq->flush_color != next->flush_color); |
| |
| list_del_init(&next->list); |
| wq->first_flusher = next; |
| |
| if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1)) |
| break; |
| |
| /* |
| * Meh... this color is already done, clear first |
| * flusher and repeat cascading. |
| */ |
| wq->first_flusher = NULL; |
| } |
| |
| out_unlock: |
| mutex_unlock(&wq->mutex); |
| } |
| EXPORT_SYMBOL(flush_workqueue); |
| |
| /** |
| * drain_workqueue - drain a workqueue |
| * @wq: workqueue to drain |
| * |
| * Wait until the workqueue becomes empty. While draining is in progress, |
| * only chain queueing is allowed. IOW, only currently pending or running |
| * work items on @wq can queue further work items on it. @wq is flushed |
| * repeatedly until it becomes empty. The number of flushing is determined |
| * by the depth of chaining and should be relatively short. Whine if it |
| * takes too long. |
| */ |
| void drain_workqueue(struct workqueue_struct *wq) |
| { |
| unsigned int flush_cnt = 0; |
| struct pool_workqueue *pwq; |
| |
| /* |
| * __queue_work() needs to test whether there are drainers, is much |
| * hotter than drain_workqueue() and already looks at @wq->flags. |
| * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers. |
| */ |
| mutex_lock(&wq->mutex); |
| if (!wq->nr_drainers++) |
| wq->flags |= __WQ_DRAINING; |
| mutex_unlock(&wq->mutex); |
| reflush: |
| flush_workqueue(wq); |
| |
| mutex_lock(&wq->mutex); |
| |
| for_each_pwq(pwq, wq) { |
| bool drained; |
| |
| spin_lock_irq(&pwq->pool->lock); |
| drained = !pwq->nr_active && list_empty(&pwq->delayed_works); |
| spin_unlock_irq(&pwq->pool->lock); |
| |
| if (drained) |
| continue; |
| |
| if (++flush_cnt == 10 || |
| (flush_cnt % 100 == 0 && flush_cnt <= 1000)) |
| pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n", |
| wq->name, flush_cnt); |
| |
| mutex_unlock(&wq->mutex); |
| goto reflush; |
| } |
| |
| if (!--wq->nr_drainers) |
| wq->flags &= ~__WQ_DRAINING; |
| mutex_unlock(&wq->mutex); |
| } |
| EXPORT_SYMBOL_GPL(drain_workqueue); |
| |
| static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr) |
| { |
| struct worker *worker = NULL; |
| struct worker_pool *pool; |
| struct pool_workqueue *pwq; |
| |
| might_sleep(); |
| |
| local_irq_disable(); |
| pool = get_work_pool(work); |
| if (!pool) { |
| local_irq_enable(); |
| return false; |
| } |
| |
| spin_lock(&pool->lock); |
| /* see the comment in try_to_grab_pending() with the same code */ |
| pwq = get_work_pwq(work); |
| if (pwq) { |
| if (unlikely(pwq->pool != pool)) |
| goto already_gone; |
| } else { |
| worker = find_worker_executing_work(pool, work); |
| if (!worker) |
| goto already_gone; |
| pwq = worker->current_pwq; |
| } |
| |
| check_flush_dependency(pwq->wq, work); |
| |
| insert_wq_barrier(pwq, barr, work, worker); |
| spin_unlock_irq(&pool->lock); |
| |
| /* |
| * Force a lock recursion deadlock when using flush_work() inside a |
| * single-threaded or rescuer equipped workqueue. |
| * |
| * For single threaded workqueues the deadlock happens when the work |
| * is after the work issuing the flush_work(). For rescuer equipped |
| * workqueues the deadlock happens when the rescuer stalls, blocking |
| * forward progress. |
| */ |
| if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer) { |
| lock_map_acquire(&pwq->wq->lockdep_map); |
| lock_map_release(&pwq->wq->lockdep_map); |
| } |
| |
| return true; |
| already_gone: |
| spin_unlock_irq(&pool->lock); |
| return false; |
| } |
| |
| /** |
| * flush_work - wait for a work to finish executing the last queueing instance |
| * @work: the work to flush |
| * |
| * Wait until @work has finished execution. @work is guaranteed to be idle |
| * on return if it hasn't been requeued since flush started. |
| * |
| * Return: |
| * %true if flush_work() waited for the work to finish execution, |
| * %false if it was already idle. |
| */ |
| bool flush_work(struct work_struct *work) |
| { |
| struct wq_barrier barr; |
| |
| if (WARN_ON(!wq_online)) |
| return false; |
| |
| lock_map_acquire(&work->lockdep_map); |
| lock_map_release(&work->lockdep_map); |
| |
| if (start_flush_work(work, &barr)) { |
| wait_for_completion(&barr.done); |
| destroy_work_on_stack(&barr.work); |
| return true; |
| } else { |
| return false; |
| } |
| } |
| EXPORT_SYMBOL_GPL(flush_work); |
| |
| struct cwt_wait { |
| wait_queue_entry_t wait; |
| struct work_struct *work; |
| }; |
| |
| static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) |
| { |
| struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait); |
| |
| if (cwait->work != key) |
| return 0; |
| return autoremove_wake_function(wait, mode, sync, key); |
| } |
| |
| static bool __cancel_work_timer(struct work_struct *work, bool is_dwork) |
| { |
| static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq); |
| unsigned long flags; |
| int ret; |
| |
| do { |
| ret = try_to_grab_pending(work, is_dwork, &flags); |
| /* |
| * If someone else is already canceling, wait for it to |
| * finish. flush_work() doesn't work for PREEMPT_NONE |
| * because we may get scheduled between @work's completion |
| * and the other canceling task resuming and clearing |
| * CANCELING - flush_work() will return false immediately |
| * as @work is no longer busy, try_to_grab_pending() will |
| * return -ENOENT as @work is still being canceled and the |
| * other canceling task won't be able to clear CANCELING as |
| * we're hogging the CPU. |
| * |
| * Let's wait for completion using a waitqueue. As this |
| * may lead to the thundering herd problem, use a custom |
| * wake function which matches @work along with exclusive |
| * wait and wakeup. |
| */ |
| if (unlikely(ret == -ENOENT)) { |
| struct cwt_wait cwait; |
| |
| init_wait(&cwait.wait); |
| cwait.wait.func = cwt_wakefn; |
| cwait.work = work; |
| |
| prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait, |
| TASK_UNINTERRUPTIBLE); |
| if (work_is_canceling(work)) |
| schedule(); |
| finish_wait(&cancel_waitq, &cwait.wait); |
| } |
| } while (unlikely(ret < 0)); |
| |
| /* tell other tasks trying to grab @work to back off */ |
| mark_work_canceling(work); |
| local_irq_restore(flags); |
| |
| /* |
| * This allows canceling during early boot. We know that @work |
| * isn't executing. |
| */ |
| if (wq_online) |
| flush_work(work); |
| |
| clear_work_data(work); |
| |
| /* |
| * Paired with prepare_to_wait() above so that either |
| * waitqueue_active() is visible here or !work_is_canceling() is |
| * visible there. |
| */ |
| smp_mb(); |
| if (waitqueue_active(&cancel_waitq)) |
| __wake_up(&cancel_waitq, TASK_NORMAL, 1, work); |
| |
| return ret; |
| } |
| |
| /** |
| * cancel_work_sync - cancel a work and wait for it to finish |
| * @work: the work to cancel |
| * |
| * Cancel @work and wait for its execution to finish. This function |
| * can be used even if the work re-queues itself or migrates to |
| * another workqueue. On return from this function, @work is |
| * guaranteed to be not pending or executing on any CPU. |
| * |
| * cancel_work_sync(&delayed_work->work) must not be used for |
| * delayed_work's. Use cancel_delayed_work_sync() instead. |
| * |
| * The caller must ensure that the workqueue on which @work was last |
| * queued can't be destroyed before this function returns. |
| * |
| * Return: |
| * %true if @work was pending, %false otherwise. |
| */ |
| bool cancel_work_sync(struct work_struct *work) |
| { |
| return __cancel_work_timer(work, false); |
| } |
| EXPORT_SYMBOL_GPL(cancel_work_sync); |
| |
| /** |
| * flush_delayed_work - wait for a dwork to finish executing the last queueing |
| * @dwork: the delayed work to flush |
| * |
| * Delayed timer is cancelled and the pending work is queued for |
| * immediate execution. Like flush_work(), this function only |
| * considers the last queueing instance of @dwork. |
| * |
| * Return: |
| * %true if flush_work() waited for the work to finish execution, |
| * %false if it was already idle. |
| */ |
| bool flush_delayed_work(struct delayed_work *dwork) |
| { |
| local_irq_disable(); |
| if (del_timer_sync(&dwork->timer)) |
| __queue_work(dwork->cpu, dwork->wq, &dwork->work); |
| local_irq_enable(); |
| return flush_work(&dwork->work); |
| } |
| EXPORT_SYMBOL(flush_delayed_work); |
| |
| static bool __cancel_work(struct work_struct *work, bool is_dwork) |
| { |
| unsigned long flags; |
| int ret; |
| |
| do { |
| ret = try_to_grab_pending(work, is_dwork, &flags); |
| } while (unlikely(ret == -EAGAIN)); |
| |
| if (unlikely(ret < 0)) |
| return false; |
| |
| set_work_pool_and_clear_pending(work, get_work_pool_id(work)); |
| local_irq_restore(flags); |
| return ret; |
| } |
| |
| /* |
| * See cancel_delayed_work() |
| */ |
| bool cancel_work(struct work_struct *work) |
| { |
| return __cancel_work(work, false); |
| } |
| |
| /** |
| * cancel_delayed_work - cancel a delayed work |
| * @dwork: delayed_work to cancel |
| * |
| * Kill off a pending delayed_work. |
| * |
| * Return: %true if @dwork was pending and canceled; %false if it wasn't |
| * pending. |
| * |
| * Note: |
| * The work callback function may still be running on return, unless |
| * it returns %true and the work doesn't re-arm itself. Explicitly flush or |
| * use cancel_delayed_work_sync() to wait on it. |
| * |
| * This function is safe to call from any context including IRQ handler. |
| */ |
| bool cancel_delayed_work(struct delayed_work *dwork) |
| { |
| return __cancel_work(&dwork->work, true); |
| } |
| EXPORT_SYMBOL(cancel_delayed_work); |
| |
| /** |
| * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish |
| * @dwork: the delayed work cancel |
| * |
| * This is cancel_work_sync() for delayed works. |
| * |
| * Return: |
| * %true if @dwork was pending, %false otherwise. |
| */ |
| bool cancel_delayed_work_sync(struct delayed_work *dwork) |
| { |
| return __cancel_work_timer(&dwork->work, true); |
| } |
| EXPORT_SYMBOL(cancel_delayed_work_sync); |
| |
| /** |
| * schedule_on_each_cpu - execute a function synchronously on each online CPU |
| * @func: the function to call |
| * |
| * schedule_on_each_cpu() executes @func on each online CPU using the |
| * system workqueue and blocks until all CPUs have completed. |
| * schedule_on_each_cpu() is very slow. |
| * |
| * Return: |
| * 0 on success, -errno on failure. |
| */ |
| int schedule_on_each_cpu(work_func_t func) |
| { |
| int cpu; |
| struct work_struct __percpu *works; |
| |
| works = alloc_percpu(struct work_struct); |
| if (!works) |
| return -ENOMEM; |
| |
| get_online_cpus(); |
| |
| for_each_online_cpu(cpu) { |
| struct work_struct *work = per_cpu_ptr(works, cpu); |
| |
| INIT_WORK(work, func); |
| schedule_work_on(cpu, work); |
| } |
| |
| for_each_online_cpu(cpu) |
| flush_work(per_cpu_ptr(works, cpu)); |
| |
| put_online_cpus(); |
| free_percpu(works); |
| return 0; |
| } |
| |
| /** |
| * execute_in_process_context - reliably execute the routine with user context |
| * @fn: the function to execute |
| * @ew: guaranteed storage for the execute work structure (must |
| * be available when the work executes) |
| * |
| * Executes the function immediately if process context is available, |
| * otherwise schedules the function for delayed execution. |
| * |
| * Return: 0 - function was executed |
| * 1 - function was scheduled for execution |
| */ |
| int execute_in_process_context(work_func_t fn, struct execute_work *ew) |
| { |
| if (!in_interrupt()) { |
| fn(&ew->work); |
| return 0; |
| } |
| |
| INIT_WORK(&ew->work, fn); |
| schedule_work(&ew->work); |
| |
| return 1; |
| } |
| EXPORT_SYMBOL_GPL(execute_in_process_context); |
| |
| /** |
| * free_workqueue_attrs - free a workqueue_attrs |
| * @attrs: workqueue_attrs to free |
| * |
| * Undo alloc_workqueue_attrs(). |
| */ |
| void free_workqueue_attrs(struct workqueue_attrs *attrs) |
| { |
| if (attrs) { |
| free_cpumask_var(attrs->cpumask); |
| kfree(attrs); |
| } |
| } |
| |
| /** |
| * alloc_workqueue_attrs - allocate a workqueue_attrs |
| * @gfp_mask: allocation mask to use |
| * |
| * Allocate a new workqueue_attrs, initialize with default settings and |
| * return it. |
| * |
| * Return: The allocated new workqueue_attr on success. %NULL on failure. |
| */ |
| struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask) |
| { |
| struct workqueue_attrs *attrs; |
| |
| attrs = kzalloc(sizeof(*attrs), gfp_mask); |
| if (!attrs) |
| goto fail; |
| if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask)) |
| goto fail; |
| |
| cpumask_copy(attrs->cpumask, cpu_possible_mask); |
| return attrs; |
| fail: |
| free_workqueue_attrs(attrs); |
| return NULL; |
| } |
| |
| static void copy_workqueue_attrs(struct workqueue_attrs *to, |
| const struct workqueue_attrs *from) |
| { |
| to->nice = from->nice; |
| cpumask_copy(to->cpumask, from->cpumask); |
| /* |
| * Unlike hash and equality test, this function doesn't ignore |
| * ->no_numa as it is used for both pool and wq attrs. Instead, |
| * get_unbound_pool() explicitly clears ->no_numa after copying. |
| */ |
| to->no_numa = from->no_numa; |
| } |
| |
| /* hash value of the content of @attr */ |
| static u32 wqattrs_hash(const struct workqueue_attrs *attrs) |
| { |
| u32 hash = 0; |
| |
| hash = jhash_1word(attrs->nice, hash); |
| hash = jhash(cpumask_bits(attrs->cpumask), |
| BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash); |
| return hash; |
| } |
| |
| /* content equality test */ |
| static bool wqattrs_equal(const struct workqueue_attrs *a, |
| const struct workqueue_attrs *b) |
| { |
| if (a->nice != b->nice) |
| return false; |
| if (!cpumask_equal(a->cpumask, b->cpumask)) |
| return false; |
| return true; |
| } |
| |
| /** |
| * init_worker_pool - initialize a newly zalloc'd worker_pool |
| * @pool: worker_pool to initialize |
| * |
| * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs. |
| * |
| * Return: 0 on success, -errno on failure. Even on failure, all fields |
| * inside @pool proper are initialized and put_unbound_pool() can be called |
| * on @pool safely to release it. |
| */ |
| static int init_worker_pool(struct worker_pool *pool) |
| { |
| spin_lock_init(&pool->lock); |
| pool->id = -1; |
| pool->cpu = -1; |
| pool->node = NUMA_NO_NODE; |
| pool->flags |= POOL_DISASSOCIATED; |
| pool->watchdog_ts = jiffies; |
| INIT_LIST_HEAD(&pool->worklist); |
| INIT_LIST_HEAD(&pool->idle_list); |
| hash_init(pool->busy_hash); |
| |
| setup_deferrable_timer(&pool->idle_timer, idle_worker_timeout, |
| (unsigned long)pool); |
| |
| setup_timer(&pool->mayday_timer, pool_mayday_timeout, |
| (unsigned long)pool); |
| |
| mutex_init(&pool->attach_mutex); |
| INIT_LIST_HEAD(&pool->workers); |
| |
| ida_init(&pool->worker_ida); |
| INIT_HLIST_NODE(&pool->hash_node); |
| pool->refcnt = 1; |
| |
| /* shouldn't fail above this point */ |
| pool->attrs = alloc_workqueue_attrs(GFP_KERNEL); |
| if (!pool->attrs) |
| return -ENOMEM; |
| return 0; |
| } |
| |
| static void rcu_free_wq(struct rcu_head *rcu) |
| { |
| struct workqueue_struct *wq = |
| container_of(rcu, struct workqueue_struct, rcu); |
| |
| if (!(wq->flags & WQ_UNBOUND)) |
| free_percpu(wq->cpu_pwqs); |
| else |
| free_workqueue_attrs(wq->unbound_attrs); |
| |
| kfree(wq->rescuer); |
| kfree(wq); |
| } |
| |
| static void rcu_free_pool(struct rcu_head *rcu) |
| { |
| struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu); |
| |
| ida_destroy(&pool->worker_ida); |
| free_workqueue_attrs(pool->attrs); |
| kfree(pool); |
| } |
| |
| /** |
| * put_unbound_pool - put a worker_pool |
| * @pool: worker_pool to put |
| * |
| * Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU |
| * safe manner. get_unbound_pool() calls this function on its failure path |
| * and this function should be able to release pools which went through, |
| * successfully or not, init_worker_pool(). |
| * |
| * Should be called with wq_pool_mutex held. |
| */ |
| static void put_unbound_pool(struct worker_pool *pool) |
| { |
| DECLARE_COMPLETION_ONSTACK(detach_completion); |
| struct worker *worker; |
| |
| lockdep_assert_held(&wq_pool_mutex); |
| |
| if (--pool->refcnt) |
| return; |
| |
| /* sanity checks */ |
| if (WARN_ON(!(pool->cpu < 0)) || |
| WARN_ON(!list_empty(&pool->worklist))) |
| return; |
| |
| /* release id and unhash */ |
| if (pool->id >= 0) |
| idr_remove(&worker_pool_idr, pool->id); |
| hash_del(&pool->hash_node); |
| |
| /* |
| * Become the manager and destroy all workers. This prevents |
| * @pool's workers from blocking on attach_mutex. We're the last |
| * manager and @pool gets freed with the flag set. |
| */ |
| spin_lock_irq(&pool->lock); |
| wait_event_lock_irq(wq_manager_wait, |
| !(pool->flags & POOL_MANAGER_ACTIVE), pool->lock); |
| pool->flags |= POOL_MANAGER_ACTIVE; |
| |
| while ((worker = first_idle_worker(pool))) |
| destroy_worker(worker); |
| WARN_ON(pool->nr_workers || pool->nr_idle); |
| spin_unlock_irq(&pool->lock); |
| |
| mutex_lock(&pool->attach_mutex); |
| if (!list_empty(&pool->workers)) |
| pool->detach_completion = &detach_completion; |
| mutex_unlock(&pool->attach_mutex); |
| |
| if (pool->detach_completion) |
| wait_for_completion(pool->detach_completion); |
| |
| /* shut down the timers */ |
| del_timer_sync(&pool->idle_timer); |
| del_timer_sync(&pool->mayday_timer); |
| |
| /* sched-RCU protected to allow dereferences from get_work_pool() */ |
| call_rcu_sched(&pool->rcu, rcu_free_pool); |
| } |
| |
| /** |
| * get_unbound_pool - get a worker_pool with the specified attributes |
| * @attrs: the attributes of the worker_pool to get |
| * |
| * Obtain a worker_pool which has the same attributes as @attrs, bump the |
| * reference count and return it. If there already is a matching |
| * worker_pool, it will be used; otherwise, this function attempts to |
| * create a new one. |
| * |
| * Should be called with wq_pool_mutex held. |
| * |
| * Return: On success, a worker_pool with the same attributes as @attrs. |
| * On failure, %NULL. |
| */ |
| static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs) |
| { |
| u32 hash = wqattrs_hash(attrs); |
| struct worker_pool *pool; |
| int node; |
| int target_node = NUMA_NO_NODE; |
| |
| lockdep_assert_held(&wq_pool_mutex); |
| |
| /* do we already have a matching pool? */ |
| hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) { |
| if (wqattrs_equal(pool->attrs, attrs)) { |
| pool->refcnt++; |
| return pool; |
| } |
| } |
| |
| /* if cpumask is contained inside a NUMA node, we belong to that node */ |
| if (wq_numa_enabled) { |
| for_each_node(node) { |
| if (cpumask_subset(attrs->cpumask, |
| wq_numa_possible_cpumask[node])) { |
| target_node = node; |
| break; |
| } |
| } |
| } |
| |
| /* nope, create a new one */ |
| pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node); |
| if (!pool || init_worker_pool(pool) < 0) |
| goto fail; |
| |
| lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */ |
| copy_workqueue_attrs(pool->attrs, attrs); |
| pool->node = target_node; |
| |
| /* |
| * no_numa isn't a worker_pool attribute, always clear it. See |
| * 'struct workqueue_attrs' comments for detail. |
| */ |
| pool->attrs->no_numa = false; |
| |
| if (worker_pool_assign_id(pool) < 0) |
| goto fail; |
| |
| /* create and start the initial worker */ |
| if (wq_online && !create_worker(pool)) |
| goto fail; |
| |
| /* install */ |
| hash_add(unbound_pool_hash, &pool->hash_node, hash); |
| |
| return pool; |
| fail: |
| if (pool) |
| put_unbound_pool(pool); |
| return NULL; |
| } |
| |
| static void rcu_free_pwq(struct rcu_head *rcu) |
| { |
| kmem_cache_free(pwq_cache, |
| container_of(rcu, struct pool_workqueue, rcu)); |
| } |
| |
| /* |
| * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt |
| * and needs to be destroyed. |
| */ |
| static void pwq_unbound_release_workfn(struct work_struct *work) |
| { |
| struct pool_workqueue *pwq = container_of(work, struct pool_workqueue, |
| unbound_release_work); |
| struct workqueue_struct *wq = pwq->wq; |
| struct worker_pool *pool = pwq->pool; |
| bool is_last; |
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