| /* |
| * kernel/mutex.c |
| * |
| * Mutexes: blocking mutual exclusion locks |
| * |
| * Started by Ingo Molnar: |
| * |
| * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> |
| * |
| * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and |
| * David Howells for suggestions and improvements. |
| * |
| * - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline |
| * from the -rt tree, where it was originally implemented for rtmutexes |
| * by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale |
| * and Sven Dietrich. |
| * |
| * Also see Documentation/mutex-design.txt. |
| */ |
| #include <linux/mutex.h> |
| #include <linux/ww_mutex.h> |
| #include <linux/sched.h> |
| #include <linux/sched/rt.h> |
| #include <linux/export.h> |
| #include <linux/spinlock.h> |
| #include <linux/interrupt.h> |
| #include <linux/debug_locks.h> |
| |
| /* |
| * In the DEBUG case we are using the "NULL fastpath" for mutexes, |
| * which forces all calls into the slowpath: |
| */ |
| #ifdef CONFIG_DEBUG_MUTEXES |
| # include "mutex-debug.h" |
| # include <asm-generic/mutex-null.h> |
| #else |
| # include "mutex.h" |
| # include <asm/mutex.h> |
| #endif |
| |
| /* |
| * A negative mutex count indicates that waiters are sleeping waiting for the |
| * mutex. |
| */ |
| #define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) >= 0) |
| |
| void |
| __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) |
| { |
| atomic_set(&lock->count, 1); |
| spin_lock_init(&lock->wait_lock); |
| INIT_LIST_HEAD(&lock->wait_list); |
| mutex_clear_owner(lock); |
| #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
| lock->spin_mlock = NULL; |
| #endif |
| |
| debug_mutex_init(lock, name, key); |
| } |
| |
| EXPORT_SYMBOL(__mutex_init); |
| |
| #ifndef CONFIG_DEBUG_LOCK_ALLOC |
| /* |
| * We split the mutex lock/unlock logic into separate fastpath and |
| * slowpath functions, to reduce the register pressure on the fastpath. |
| * We also put the fastpath first in the kernel image, to make sure the |
| * branch is predicted by the CPU as default-untaken. |
| */ |
| static __used noinline void __sched |
| __mutex_lock_slowpath(atomic_t *lock_count); |
| |
| /** |
| * mutex_lock - acquire the mutex |
| * @lock: the mutex to be acquired |
| * |
| * Lock the mutex exclusively for this task. If the mutex is not |
| * available right now, it will sleep until it can get it. |
| * |
| * The mutex must later on be released by the same task that |
| * acquired it. Recursive locking is not allowed. The task |
| * may not exit without first unlocking the mutex. Also, kernel |
| * memory where the mutex resides mutex must not be freed with |
| * the mutex still locked. The mutex must first be initialized |
| * (or statically defined) before it can be locked. memset()-ing |
| * the mutex to 0 is not allowed. |
| * |
| * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging |
| * checks that will enforce the restrictions and will also do |
| * deadlock debugging. ) |
| * |
| * This function is similar to (but not equivalent to) down(). |
| */ |
| void __sched mutex_lock(struct mutex *lock) |
| { |
| might_sleep(); |
| /* |
| * The locking fastpath is the 1->0 transition from |
| * 'unlocked' into 'locked' state. |
| */ |
| __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath); |
| mutex_set_owner(lock); |
| } |
| |
| EXPORT_SYMBOL(mutex_lock); |
| #endif |
| |
| #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
| /* |
| * In order to avoid a stampede of mutex spinners from acquiring the mutex |
| * more or less simultaneously, the spinners need to acquire a MCS lock |
| * first before spinning on the owner field. |
| * |
| * We don't inline mspin_lock() so that perf can correctly account for the |
| * time spent in this lock function. |
| */ |
| struct mspin_node { |
| struct mspin_node *next ; |
| int locked; /* 1 if lock acquired */ |
| }; |
| #define MLOCK(mutex) ((struct mspin_node **)&((mutex)->spin_mlock)) |
| |
| static noinline |
| void mspin_lock(struct mspin_node **lock, struct mspin_node *node) |
| { |
| struct mspin_node *prev; |
| |
| /* Init node */ |
| node->locked = 0; |
| node->next = NULL; |
| |
| prev = xchg(lock, node); |
| if (likely(prev == NULL)) { |
| /* Lock acquired */ |
| node->locked = 1; |
| return; |
| } |
| ACCESS_ONCE(prev->next) = node; |
| smp_wmb(); |
| /* Wait until the lock holder passes the lock down */ |
| while (!ACCESS_ONCE(node->locked)) |
| arch_mutex_cpu_relax(); |
| } |
| |
| static void mspin_unlock(struct mspin_node **lock, struct mspin_node *node) |
| { |
| struct mspin_node *next = ACCESS_ONCE(node->next); |
| |
| if (likely(!next)) { |
| /* |
| * Release the lock by setting it to NULL |
| */ |
| if (cmpxchg(lock, node, NULL) == node) |
| return; |
| /* Wait until the next pointer is set */ |
| while (!(next = ACCESS_ONCE(node->next))) |
| arch_mutex_cpu_relax(); |
| } |
| ACCESS_ONCE(next->locked) = 1; |
| smp_wmb(); |
| } |
| |
| /* |
| * Mutex spinning code migrated from kernel/sched/core.c |
| */ |
| |
| static inline bool owner_running(struct mutex *lock, struct task_struct *owner) |
| { |
| if (lock->owner != owner) |
| return false; |
| |
| /* |
| * Ensure we emit the owner->on_cpu, dereference _after_ checking |
| * lock->owner still matches owner, if that fails, owner might |
| * point to free()d memory, if it still matches, the rcu_read_lock() |
| * ensures the memory stays valid. |
| */ |
| barrier(); |
| |
| return owner->on_cpu; |
| } |
| |
| /* |
| * Look out! "owner" is an entirely speculative pointer |
| * access and not reliable. |
| */ |
| static noinline |
| int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) |
| { |
| rcu_read_lock(); |
| while (owner_running(lock, owner)) { |
| if (need_resched()) |
| break; |
| |
| arch_mutex_cpu_relax(); |
| } |
| rcu_read_unlock(); |
| |
| /* |
| * We break out the loop above on need_resched() and when the |
| * owner changed, which is a sign for heavy contention. Return |
| * success only when lock->owner is NULL. |
| */ |
| return lock->owner == NULL; |
| } |
| |
| /* |
| * Initial check for entering the mutex spinning loop |
| */ |
| static inline int mutex_can_spin_on_owner(struct mutex *lock) |
| { |
| int retval = 1; |
| |
| rcu_read_lock(); |
| if (lock->owner) |
| retval = lock->owner->on_cpu; |
| rcu_read_unlock(); |
| /* |
| * if lock->owner is not set, the mutex owner may have just acquired |
| * it and not set the owner yet or the mutex has been released. |
| */ |
| return retval; |
| } |
| #endif |
| |
| static __used noinline void __sched __mutex_unlock_slowpath(atomic_t *lock_count); |
| |
| /** |
| * mutex_unlock - release the mutex |
| * @lock: the mutex to be released |
| * |
| * Unlock a mutex that has been locked by this task previously. |
| * |
| * This function must not be used in interrupt context. Unlocking |
| * of a not locked mutex is not allowed. |
| * |
| * This function is similar to (but not equivalent to) up(). |
| */ |
| void __sched mutex_unlock(struct mutex *lock) |
| { |
| /* |
| * The unlocking fastpath is the 0->1 transition from 'locked' |
| * into 'unlocked' state: |
| */ |
| #ifndef CONFIG_DEBUG_MUTEXES |
| /* |
| * When debugging is enabled we must not clear the owner before time, |
| * the slow path will always be taken, and that clears the owner field |
| * after verifying that it was indeed current. |
| */ |
| mutex_clear_owner(lock); |
| #endif |
| __mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath); |
| } |
| |
| EXPORT_SYMBOL(mutex_unlock); |
| |
| /** |
| * ww_mutex_unlock - release the w/w mutex |
| * @lock: the mutex to be released |
| * |
| * Unlock a mutex that has been locked by this task previously with any of the |
| * ww_mutex_lock* functions (with or without an acquire context). It is |
| * forbidden to release the locks after releasing the acquire context. |
| * |
| * This function must not be used in interrupt context. Unlocking |
| * of a unlocked mutex is not allowed. |
| */ |
| void __sched ww_mutex_unlock(struct ww_mutex *lock) |
| { |
| /* |
| * The unlocking fastpath is the 0->1 transition from 'locked' |
| * into 'unlocked' state: |
| */ |
| if (lock->ctx) { |
| #ifdef CONFIG_DEBUG_MUTEXES |
| DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired); |
| #endif |
| if (lock->ctx->acquired > 0) |
| lock->ctx->acquired--; |
| lock->ctx = NULL; |
| } |
| |
| #ifndef CONFIG_DEBUG_MUTEXES |
| /* |
| * When debugging is enabled we must not clear the owner before time, |
| * the slow path will always be taken, and that clears the owner field |
| * after verifying that it was indeed current. |
| */ |
| mutex_clear_owner(&lock->base); |
| #endif |
| __mutex_fastpath_unlock(&lock->base.count, __mutex_unlock_slowpath); |
| } |
| EXPORT_SYMBOL(ww_mutex_unlock); |
| |
| static inline int __sched |
| __mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx) |
| { |
| struct ww_mutex *ww = container_of(lock, struct ww_mutex, base); |
| struct ww_acquire_ctx *hold_ctx = ACCESS_ONCE(ww->ctx); |
| |
| if (!hold_ctx) |
| return 0; |
| |
| if (unlikely(ctx == hold_ctx)) |
| return -EALREADY; |
| |
| if (ctx->stamp - hold_ctx->stamp <= LONG_MAX && |
| (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) { |
| #ifdef CONFIG_DEBUG_MUTEXES |
| DEBUG_LOCKS_WARN_ON(ctx->contending_lock); |
| ctx->contending_lock = ww; |
| #endif |
| return -EDEADLK; |
| } |
| |
| return 0; |
| } |
| |
| static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww, |
| struct ww_acquire_ctx *ww_ctx) |
| { |
| #ifdef CONFIG_DEBUG_MUTEXES |
| /* |
| * If this WARN_ON triggers, you used ww_mutex_lock to acquire, |
| * but released with a normal mutex_unlock in this call. |
| * |
| * This should never happen, always use ww_mutex_unlock. |
| */ |
| DEBUG_LOCKS_WARN_ON(ww->ctx); |
| |
| /* |
| * Not quite done after calling ww_acquire_done() ? |
| */ |
| DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire); |
| |
| if (ww_ctx->contending_lock) { |
| /* |
| * After -EDEADLK you tried to |
| * acquire a different ww_mutex? Bad! |
| */ |
| DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww); |
| |
| /* |
| * You called ww_mutex_lock after receiving -EDEADLK, |
| * but 'forgot' to unlock everything else first? |
| */ |
| DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0); |
| ww_ctx->contending_lock = NULL; |
| } |
| |
| /* |
| * Naughty, using a different class will lead to undefined behavior! |
| */ |
| DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class); |
| #endif |
| ww_ctx->acquired++; |
| } |
| |
| /* |
| * after acquiring lock with fastpath or when we lost out in contested |
| * slowpath, set ctx and wake up any waiters so they can recheck. |
| * |
| * This function is never called when CONFIG_DEBUG_LOCK_ALLOC is set, |
| * as the fastpath and opportunistic spinning are disabled in that case. |
| */ |
| static __always_inline void |
| ww_mutex_set_context_fastpath(struct ww_mutex *lock, |
| struct ww_acquire_ctx *ctx) |
| { |
| unsigned long flags; |
| struct mutex_waiter *cur; |
| |
| ww_mutex_lock_acquired(lock, ctx); |
| |
| lock->ctx = ctx; |
| |
| /* |
| * The lock->ctx update should be visible on all cores before |
| * the atomic read is done, otherwise contended waiters might be |
| * missed. The contended waiters will either see ww_ctx == NULL |
| * and keep spinning, or it will acquire wait_lock, add itself |
| * to waiter list and sleep. |
| */ |
| smp_mb(); /* ^^^ */ |
| |
| /* |
| * Check if lock is contended, if not there is nobody to wake up |
| */ |
| if (likely(atomic_read(&lock->base.count) == 0)) |
| return; |
| |
| /* |
| * Uh oh, we raced in fastpath, wake up everyone in this case, |
| * so they can see the new lock->ctx. |
| */ |
| spin_lock_mutex(&lock->base.wait_lock, flags); |
| list_for_each_entry(cur, &lock->base.wait_list, list) { |
| debug_mutex_wake_waiter(&lock->base, cur); |
| wake_up_process(cur->task); |
| } |
| spin_unlock_mutex(&lock->base.wait_lock, flags); |
| } |
| |
| /* |
| * Lock a mutex (possibly interruptible), slowpath: |
| */ |
| static __always_inline int __sched |
| __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, |
| struct lockdep_map *nest_lock, unsigned long ip, |
| struct ww_acquire_ctx *ww_ctx) |
| { |
| struct task_struct *task = current; |
| struct mutex_waiter waiter; |
| unsigned long flags; |
| int ret; |
| |
| preempt_disable(); |
| mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); |
| |
| #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
| /* |
| * Optimistic spinning. |
| * |
| * We try to spin for acquisition when we find that there are no |
| * pending waiters and the lock owner is currently running on a |
| * (different) CPU. |
| * |
| * The rationale is that if the lock owner is running, it is likely to |
| * release the lock soon. |
| * |
| * Since this needs the lock owner, and this mutex implementation |
| * doesn't track the owner atomically in the lock field, we need to |
| * track it non-atomically. |
| * |
| * We can't do this for DEBUG_MUTEXES because that relies on wait_lock |
| * to serialize everything. |
| * |
| * The mutex spinners are queued up using MCS lock so that only one |
| * spinner can compete for the mutex. However, if mutex spinning isn't |
| * going to happen, there is no point in going through the lock/unlock |
| * overhead. |
| */ |
| if (!mutex_can_spin_on_owner(lock)) |
| goto slowpath; |
| |
| for (;;) { |
| struct task_struct *owner; |
| struct mspin_node node; |
| |
| if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) { |
| struct ww_mutex *ww; |
| |
| ww = container_of(lock, struct ww_mutex, base); |
| /* |
| * If ww->ctx is set the contents are undefined, only |
| * by acquiring wait_lock there is a guarantee that |
| * they are not invalid when reading. |
| * |
| * As such, when deadlock detection needs to be |
| * performed the optimistic spinning cannot be done. |
| */ |
| if (ACCESS_ONCE(ww->ctx)) |
| break; |
| } |
| |
| /* |
| * If there's an owner, wait for it to either |
| * release the lock or go to sleep. |
| */ |
| mspin_lock(MLOCK(lock), &node); |
| owner = ACCESS_ONCE(lock->owner); |
| if (owner && !mutex_spin_on_owner(lock, owner)) { |
| mspin_unlock(MLOCK(lock), &node); |
| break; |
| } |
| |
| if ((atomic_read(&lock->count) == 1) && |
| (atomic_cmpxchg(&lock->count, 1, 0) == 1)) { |
| lock_acquired(&lock->dep_map, ip); |
| if (!__builtin_constant_p(ww_ctx == NULL)) { |
| struct ww_mutex *ww; |
| ww = container_of(lock, struct ww_mutex, base); |
| |
| ww_mutex_set_context_fastpath(ww, ww_ctx); |
| } |
| |
| mutex_set_owner(lock); |
| mspin_unlock(MLOCK(lock), &node); |
| preempt_enable(); |
| return 0; |
| } |
| mspin_unlock(MLOCK(lock), &node); |
| |
| /* |
| * When there's no owner, we might have preempted between the |
| * owner acquiring the lock and setting the owner field. If |
| * we're an RT task that will live-lock because we won't let |
| * the owner complete. |
| */ |
| if (!owner && (need_resched() || rt_task(task))) |
| break; |
| |
| /* |
| * The cpu_relax() call is a compiler barrier which forces |
| * everything in this loop to be re-loaded. We don't need |
| * memory barriers as we'll eventually observe the right |
| * values at the cost of a few extra spins. |
| */ |
| arch_mutex_cpu_relax(); |
| } |
| slowpath: |
| #endif |
| spin_lock_mutex(&lock->wait_lock, flags); |
| |
| debug_mutex_lock_common(lock, &waiter); |
| debug_mutex_add_waiter(lock, &waiter, task_thread_info(task)); |
| |
| /* add waiting tasks to the end of the waitqueue (FIFO): */ |
| list_add_tail(&waiter.list, &lock->wait_list); |
| waiter.task = task; |
| |
| if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, -1) == 1)) |
| goto done; |
| |
| lock_contended(&lock->dep_map, ip); |
| |
| for (;;) { |
| /* |
| * Lets try to take the lock again - this is needed even if |
| * we get here for the first time (shortly after failing to |
| * acquire the lock), to make sure that we get a wakeup once |
| * it's unlocked. Later on, if we sleep, this is the |
| * operation that gives us the lock. We xchg it to -1, so |
| * that when we release the lock, we properly wake up the |
| * other waiters: |
| */ |
| if (MUTEX_SHOW_NO_WAITER(lock) && |
| (atomic_xchg(&lock->count, -1) == 1)) |
| break; |
| |
| /* |
| * got a signal? (This code gets eliminated in the |
| * TASK_UNINTERRUPTIBLE case.) |
| */ |
| if (unlikely(signal_pending_state(state, task))) { |
| ret = -EINTR; |
| goto err; |
| } |
| |
| if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) { |
| ret = __mutex_lock_check_stamp(lock, ww_ctx); |
| if (ret) |
| goto err; |
| } |
| |
| __set_task_state(task, state); |
| |
| /* didn't get the lock, go to sleep: */ |
| spin_unlock_mutex(&lock->wait_lock, flags); |
| schedule_preempt_disabled(); |
| spin_lock_mutex(&lock->wait_lock, flags); |
| } |
| |
| done: |
| lock_acquired(&lock->dep_map, ip); |
| /* got the lock - rejoice! */ |
| mutex_remove_waiter(lock, &waiter, current_thread_info()); |
| mutex_set_owner(lock); |
| |
| if (!__builtin_constant_p(ww_ctx == NULL)) { |
| struct ww_mutex *ww = container_of(lock, |
| struct ww_mutex, |
| base); |
| struct mutex_waiter *cur; |
| |
| /* |
| * This branch gets optimized out for the common case, |
| * and is only important for ww_mutex_lock. |
| */ |
| |
| ww_mutex_lock_acquired(ww, ww_ctx); |
| ww->ctx = ww_ctx; |
| |
| /* |
| * Give any possible sleeping processes the chance to wake up, |
| * so they can recheck if they have to back off. |
| */ |
| list_for_each_entry(cur, &lock->wait_list, list) { |
| debug_mutex_wake_waiter(lock, cur); |
| wake_up_process(cur->task); |
| } |
| } |
| |
| /* set it to 0 if there are no waiters left: */ |
| if (likely(list_empty(&lock->wait_list))) |
| atomic_set(&lock->count, 0); |
| |
| spin_unlock_mutex(&lock->wait_lock, flags); |
| |
| debug_mutex_free_waiter(&waiter); |
| preempt_enable(); |
| |
| return 0; |
| |
| err: |
| mutex_remove_waiter(lock, &waiter, task_thread_info(task)); |
| spin_unlock_mutex(&lock->wait_lock, flags); |
| debug_mutex_free_waiter(&waiter); |
| mutex_release(&lock->dep_map, 1, ip); |
| preempt_enable(); |
| return ret; |
| } |
| |
| #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| void __sched |
| mutex_lock_nested(struct mutex *lock, unsigned int subclass) |
| { |
| might_sleep(); |
| __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, |
| subclass, NULL, _RET_IP_, NULL); |
| } |
| |
| EXPORT_SYMBOL_GPL(mutex_lock_nested); |
| |
| void __sched |
| _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest) |
| { |
| might_sleep(); |
| __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, |
| 0, nest, _RET_IP_, NULL); |
| } |
| |
| EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock); |
| |
| int __sched |
| mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) |
| { |
| might_sleep(); |
| return __mutex_lock_common(lock, TASK_KILLABLE, |
| subclass, NULL, _RET_IP_, NULL); |
| } |
| EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); |
| |
| int __sched |
| mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) |
| { |
| might_sleep(); |
| return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, |
| subclass, NULL, _RET_IP_, NULL); |
| } |
| |
| EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested); |
| |
| static inline int |
| ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
| { |
| #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH |
| unsigned tmp; |
| |
| if (ctx->deadlock_inject_countdown-- == 0) { |
| tmp = ctx->deadlock_inject_interval; |
| if (tmp > UINT_MAX/4) |
| tmp = UINT_MAX; |
| else |
| tmp = tmp*2 + tmp + tmp/2; |
| |
| ctx->deadlock_inject_interval = tmp; |
| ctx->deadlock_inject_countdown = tmp; |
| ctx->contending_lock = lock; |
| |
| ww_mutex_unlock(lock); |
| |
| return -EDEADLK; |
| } |
| #endif |
| |
| return 0; |
| } |
| |
| int __sched |
| __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
| { |
| int ret; |
| |
| might_sleep(); |
| ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, |
| 0, &ctx->dep_map, _RET_IP_, ctx); |
| if (!ret && ctx->acquired > 0) |
| return ww_mutex_deadlock_injection(lock, ctx); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(__ww_mutex_lock); |
| |
| int __sched |
| __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
| { |
| int ret; |
| |
| might_sleep(); |
| ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, |
| 0, &ctx->dep_map, _RET_IP_, ctx); |
| |
| if (!ret && ctx->acquired > 0) |
| return ww_mutex_deadlock_injection(lock, ctx); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible); |
| |
| #endif |
| |
| /* |
| * Release the lock, slowpath: |
| */ |
| static inline void |
| __mutex_unlock_common_slowpath(atomic_t *lock_count, int nested) |
| { |
| struct mutex *lock = container_of(lock_count, struct mutex, count); |
| unsigned long flags; |
| |
| spin_lock_mutex(&lock->wait_lock, flags); |
| mutex_release(&lock->dep_map, nested, _RET_IP_); |
| debug_mutex_unlock(lock); |
| |
| /* |
| * some architectures leave the lock unlocked in the fastpath failure |
| * case, others need to leave it locked. In the later case we have to |
| * unlock it here |
| */ |
| if (__mutex_slowpath_needs_to_unlock()) |
| atomic_set(&lock->count, 1); |
| |
| if (!list_empty(&lock->wait_list)) { |
| /* get the first entry from the wait-list: */ |
| struct mutex_waiter *waiter = |
| list_entry(lock->wait_list.next, |
| struct mutex_waiter, list); |
| |
| debug_mutex_wake_waiter(lock, waiter); |
| |
| wake_up_process(waiter->task); |
| } |
| |
| spin_unlock_mutex(&lock->wait_lock, flags); |
| } |
| |
| /* |
| * Release the lock, slowpath: |
| */ |
| static __used noinline void |
| __mutex_unlock_slowpath(atomic_t *lock_count) |
| { |
| __mutex_unlock_common_slowpath(lock_count, 1); |
| } |
| |
| #ifndef CONFIG_DEBUG_LOCK_ALLOC |
| /* |
| * Here come the less common (and hence less performance-critical) APIs: |
| * mutex_lock_interruptible() and mutex_trylock(). |
| */ |
| static noinline int __sched |
| __mutex_lock_killable_slowpath(struct mutex *lock); |
| |
| static noinline int __sched |
| __mutex_lock_interruptible_slowpath(struct mutex *lock); |
| |
| /** |
| * mutex_lock_interruptible - acquire the mutex, interruptible |
| * @lock: the mutex to be acquired |
| * |
| * Lock the mutex like mutex_lock(), and return 0 if the mutex has |
| * been acquired or sleep until the mutex becomes available. If a |
| * signal arrives while waiting for the lock then this function |
| * returns -EINTR. |
| * |
| * This function is similar to (but not equivalent to) down_interruptible(). |
| */ |
| int __sched mutex_lock_interruptible(struct mutex *lock) |
| { |
| int ret; |
| |
| might_sleep(); |
| ret = __mutex_fastpath_lock_retval(&lock->count); |
| if (likely(!ret)) { |
| mutex_set_owner(lock); |
| return 0; |
| } else |
| return __mutex_lock_interruptible_slowpath(lock); |
| } |
| |
| EXPORT_SYMBOL(mutex_lock_interruptible); |
| |
| int __sched mutex_lock_killable(struct mutex *lock) |
| { |
| int ret; |
| |
| might_sleep(); |
| ret = __mutex_fastpath_lock_retval(&lock->count); |
| if (likely(!ret)) { |
| mutex_set_owner(lock); |
| return 0; |
| } else |
| return __mutex_lock_killable_slowpath(lock); |
| } |
| EXPORT_SYMBOL(mutex_lock_killable); |
| |
| static __used noinline void __sched |
| __mutex_lock_slowpath(atomic_t *lock_count) |
| { |
| struct mutex *lock = container_of(lock_count, struct mutex, count); |
| |
| __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, |
| NULL, _RET_IP_, NULL); |
| } |
| |
| static noinline int __sched |
| __mutex_lock_killable_slowpath(struct mutex *lock) |
| { |
| return __mutex_lock_common(lock, TASK_KILLABLE, 0, |
| NULL, _RET_IP_, NULL); |
| } |
| |
| static noinline int __sched |
| __mutex_lock_interruptible_slowpath(struct mutex *lock) |
| { |
| return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, |
| NULL, _RET_IP_, NULL); |
| } |
| |
| static noinline int __sched |
| __ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
| { |
| return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0, |
| NULL, _RET_IP_, ctx); |
| } |
| |
| static noinline int __sched |
| __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock, |
| struct ww_acquire_ctx *ctx) |
| { |
| return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0, |
| NULL, _RET_IP_, ctx); |
| } |
| |
| #endif |
| |
| /* |
| * Spinlock based trylock, we take the spinlock and check whether we |
| * can get the lock: |
| */ |
| static inline int __mutex_trylock_slowpath(atomic_t *lock_count) |
| { |
| struct mutex *lock = container_of(lock_count, struct mutex, count); |
| unsigned long flags; |
| int prev; |
| |
| spin_lock_mutex(&lock->wait_lock, flags); |
| |
| prev = atomic_xchg(&lock->count, -1); |
| if (likely(prev == 1)) { |
| mutex_set_owner(lock); |
| mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); |
| } |
| |
| /* Set it back to 0 if there are no waiters: */ |
| if (likely(list_empty(&lock->wait_list))) |
| atomic_set(&lock->count, 0); |
| |
| spin_unlock_mutex(&lock->wait_lock, flags); |
| |
| return prev == 1; |
| } |
| |
| /** |
| * mutex_trylock - try to acquire the mutex, without waiting |
| * @lock: the mutex to be acquired |
| * |
| * Try to acquire the mutex atomically. Returns 1 if the mutex |
| * has been acquired successfully, and 0 on contention. |
| * |
| * NOTE: this function follows the spin_trylock() convention, so |
| * it is negated from the down_trylock() return values! Be careful |
| * about this when converting semaphore users to mutexes. |
| * |
| * This function must not be used in interrupt context. The |
| * mutex must be released by the same task that acquired it. |
| */ |
| int __sched mutex_trylock(struct mutex *lock) |
| { |
| int ret; |
| |
| ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath); |
| if (ret) |
| mutex_set_owner(lock); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL(mutex_trylock); |
| |
| #ifndef CONFIG_DEBUG_LOCK_ALLOC |
| int __sched |
| __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
| { |
| int ret; |
| |
| might_sleep(); |
| |
| ret = __mutex_fastpath_lock_retval(&lock->base.count); |
| |
| if (likely(!ret)) { |
| ww_mutex_set_context_fastpath(lock, ctx); |
| mutex_set_owner(&lock->base); |
| } else |
| ret = __ww_mutex_lock_slowpath(lock, ctx); |
| return ret; |
| } |
| EXPORT_SYMBOL(__ww_mutex_lock); |
| |
| int __sched |
| __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
| { |
| int ret; |
| |
| might_sleep(); |
| |
| ret = __mutex_fastpath_lock_retval(&lock->base.count); |
| |
| if (likely(!ret)) { |
| ww_mutex_set_context_fastpath(lock, ctx); |
| mutex_set_owner(&lock->base); |
| } else |
| ret = __ww_mutex_lock_interruptible_slowpath(lock, ctx); |
| return ret; |
| } |
| EXPORT_SYMBOL(__ww_mutex_lock_interruptible); |
| |
| #endif |
| |
| /** |
| * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 |
| * @cnt: the atomic which we are to dec |
| * @lock: the mutex to return holding if we dec to 0 |
| * |
| * return true and hold lock if we dec to 0, return false otherwise |
| */ |
| int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) |
| { |
| /* dec if we can't possibly hit 0 */ |
| if (atomic_add_unless(cnt, -1, 1)) |
| return 0; |
| /* we might hit 0, so take the lock */ |
| mutex_lock(lock); |
| if (!atomic_dec_and_test(cnt)) { |
| /* when we actually did the dec, we didn't hit 0 */ |
| mutex_unlock(lock); |
| return 0; |
| } |
| /* we hit 0, and we hold the lock */ |
| return 1; |
| } |
| EXPORT_SYMBOL(atomic_dec_and_mutex_lock); |