| /* |
| * Sleepable Read-Copy Update mechanism for mutual exclusion. |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, you can access it online at |
| * http://www.gnu.org/licenses/gpl-2.0.html. |
| * |
| * Copyright (C) IBM Corporation, 2006 |
| * Copyright (C) Fujitsu, 2012 |
| * |
| * Author: Paul McKenney <paulmck@us.ibm.com> |
| * Lai Jiangshan <laijs@cn.fujitsu.com> |
| * |
| * For detailed explanation of Read-Copy Update mechanism see - |
| * Documentation/RCU/ *.txt |
| * |
| */ |
| |
| #include <linux/export.h> |
| #include <linux/mutex.h> |
| #include <linux/percpu.h> |
| #include <linux/preempt.h> |
| #include <linux/rcupdate_wait.h> |
| #include <linux/sched.h> |
| #include <linux/smp.h> |
| #include <linux/delay.h> |
| #include <linux/module.h> |
| #include <linux/srcu.h> |
| |
| #include "rcu.h" |
| #include "rcu_segcblist.h" |
| |
| ulong exp_holdoff = 25 * 1000; /* Holdoff (ns) for auto-expediting. */ |
| module_param(exp_holdoff, ulong, 0444); |
| |
| static void srcu_invoke_callbacks(struct work_struct *work); |
| static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay); |
| |
| /* |
| * Initialize SRCU combining tree. Note that statically allocated |
| * srcu_struct structures might already have srcu_read_lock() and |
| * srcu_read_unlock() running against them. So if the is_static parameter |
| * is set, don't initialize ->srcu_lock_count[] and ->srcu_unlock_count[]. |
| */ |
| static void init_srcu_struct_nodes(struct srcu_struct *sp, bool is_static) |
| { |
| int cpu; |
| int i; |
| int level = 0; |
| int levelspread[RCU_NUM_LVLS]; |
| struct srcu_data *sdp; |
| struct srcu_node *snp; |
| struct srcu_node *snp_first; |
| |
| /* Work out the overall tree geometry. */ |
| sp->level[0] = &sp->node[0]; |
| for (i = 1; i < rcu_num_lvls; i++) |
| sp->level[i] = sp->level[i - 1] + num_rcu_lvl[i - 1]; |
| rcu_init_levelspread(levelspread, num_rcu_lvl); |
| |
| /* Each pass through this loop initializes one srcu_node structure. */ |
| rcu_for_each_node_breadth_first(sp, snp) { |
| spin_lock_init(&snp->lock); |
| WARN_ON_ONCE(ARRAY_SIZE(snp->srcu_have_cbs) != |
| ARRAY_SIZE(snp->srcu_data_have_cbs)); |
| for (i = 0; i < ARRAY_SIZE(snp->srcu_have_cbs); i++) { |
| snp->srcu_have_cbs[i] = 0; |
| snp->srcu_data_have_cbs[i] = 0; |
| } |
| snp->srcu_gp_seq_needed_exp = 0; |
| snp->grplo = -1; |
| snp->grphi = -1; |
| if (snp == &sp->node[0]) { |
| /* Root node, special case. */ |
| snp->srcu_parent = NULL; |
| continue; |
| } |
| |
| /* Non-root node. */ |
| if (snp == sp->level[level + 1]) |
| level++; |
| snp->srcu_parent = sp->level[level - 1] + |
| (snp - sp->level[level]) / |
| levelspread[level - 1]; |
| } |
| |
| /* |
| * Initialize the per-CPU srcu_data array, which feeds into the |
| * leaves of the srcu_node tree. |
| */ |
| WARN_ON_ONCE(ARRAY_SIZE(sdp->srcu_lock_count) != |
| ARRAY_SIZE(sdp->srcu_unlock_count)); |
| level = rcu_num_lvls - 1; |
| snp_first = sp->level[level]; |
| for_each_possible_cpu(cpu) { |
| sdp = per_cpu_ptr(sp->sda, cpu); |
| spin_lock_init(&sdp->lock); |
| rcu_segcblist_init(&sdp->srcu_cblist); |
| sdp->srcu_cblist_invoking = false; |
| sdp->srcu_gp_seq_needed = sp->srcu_gp_seq; |
| sdp->srcu_gp_seq_needed_exp = sp->srcu_gp_seq; |
| sdp->mynode = &snp_first[cpu / levelspread[level]]; |
| for (snp = sdp->mynode; snp != NULL; snp = snp->srcu_parent) { |
| if (snp->grplo < 0) |
| snp->grplo = cpu; |
| snp->grphi = cpu; |
| } |
| sdp->cpu = cpu; |
| INIT_DELAYED_WORK(&sdp->work, srcu_invoke_callbacks); |
| sdp->sp = sp; |
| sdp->grpmask = 1 << (cpu - sdp->mynode->grplo); |
| if (is_static) |
| continue; |
| |
| /* Dynamically allocated, better be no srcu_read_locks()! */ |
| for (i = 0; i < ARRAY_SIZE(sdp->srcu_lock_count); i++) { |
| sdp->srcu_lock_count[i] = 0; |
| sdp->srcu_unlock_count[i] = 0; |
| } |
| } |
| } |
| |
| /* |
| * Initialize non-compile-time initialized fields, including the |
| * associated srcu_node and srcu_data structures. The is_static |
| * parameter is passed through to init_srcu_struct_nodes(), and |
| * also tells us that ->sda has already been wired up to srcu_data. |
| */ |
| static int init_srcu_struct_fields(struct srcu_struct *sp, bool is_static) |
| { |
| mutex_init(&sp->srcu_cb_mutex); |
| mutex_init(&sp->srcu_gp_mutex); |
| sp->srcu_idx = 0; |
| sp->srcu_gp_seq = 0; |
| sp->srcu_barrier_seq = 0; |
| mutex_init(&sp->srcu_barrier_mutex); |
| atomic_set(&sp->srcu_barrier_cpu_cnt, 0); |
| INIT_DELAYED_WORK(&sp->work, process_srcu); |
| if (!is_static) |
| sp->sda = alloc_percpu(struct srcu_data); |
| init_srcu_struct_nodes(sp, is_static); |
| sp->srcu_gp_seq_needed_exp = 0; |
| sp->srcu_last_gp_end = ktime_get_mono_fast_ns(); |
| smp_store_release(&sp->srcu_gp_seq_needed, 0); /* Init done. */ |
| return sp->sda ? 0 : -ENOMEM; |
| } |
| |
| #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| |
| int __init_srcu_struct(struct srcu_struct *sp, const char *name, |
| struct lock_class_key *key) |
| { |
| /* Don't re-initialize a lock while it is held. */ |
| debug_check_no_locks_freed((void *)sp, sizeof(*sp)); |
| lockdep_init_map(&sp->dep_map, name, key, 0); |
| spin_lock_init(&sp->gp_lock); |
| return init_srcu_struct_fields(sp, false); |
| } |
| EXPORT_SYMBOL_GPL(__init_srcu_struct); |
| |
| #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| |
| /** |
| * init_srcu_struct - initialize a sleep-RCU structure |
| * @sp: structure to initialize. |
| * |
| * Must invoke this on a given srcu_struct before passing that srcu_struct |
| * to any other function. Each srcu_struct represents a separate domain |
| * of SRCU protection. |
| */ |
| int init_srcu_struct(struct srcu_struct *sp) |
| { |
| spin_lock_init(&sp->gp_lock); |
| return init_srcu_struct_fields(sp, false); |
| } |
| EXPORT_SYMBOL_GPL(init_srcu_struct); |
| |
| #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| |
| /* |
| * First-use initialization of statically allocated srcu_struct |
| * structure. Wiring up the combining tree is more than can be |
| * done with compile-time initialization, so this check is added |
| * to each update-side SRCU primitive. Use ->gp_lock, which -is- |
| * compile-time initialized, to resolve races involving multiple |
| * CPUs trying to garner first-use privileges. |
| */ |
| static void check_init_srcu_struct(struct srcu_struct *sp) |
| { |
| unsigned long flags; |
| |
| WARN_ON_ONCE(rcu_scheduler_active == RCU_SCHEDULER_INIT); |
| /* The smp_load_acquire() pairs with the smp_store_release(). */ |
| if (!rcu_seq_state(smp_load_acquire(&sp->srcu_gp_seq_needed))) /*^^^*/ |
| return; /* Already initialized. */ |
| spin_lock_irqsave(&sp->gp_lock, flags); |
| if (!rcu_seq_state(sp->srcu_gp_seq_needed)) { |
| spin_unlock_irqrestore(&sp->gp_lock, flags); |
| return; |
| } |
| init_srcu_struct_fields(sp, true); |
| spin_unlock_irqrestore(&sp->gp_lock, flags); |
| } |
| |
| /* |
| * Returns approximate total of the readers' ->srcu_lock_count[] values |
| * for the rank of per-CPU counters specified by idx. |
| */ |
| static unsigned long srcu_readers_lock_idx(struct srcu_struct *sp, int idx) |
| { |
| int cpu; |
| unsigned long sum = 0; |
| |
| for_each_possible_cpu(cpu) { |
| struct srcu_data *cpuc = per_cpu_ptr(sp->sda, cpu); |
| |
| sum += READ_ONCE(cpuc->srcu_lock_count[idx]); |
| } |
| return sum; |
| } |
| |
| /* |
| * Returns approximate total of the readers' ->srcu_unlock_count[] values |
| * for the rank of per-CPU counters specified by idx. |
| */ |
| static unsigned long srcu_readers_unlock_idx(struct srcu_struct *sp, int idx) |
| { |
| int cpu; |
| unsigned long sum = 0; |
| |
| for_each_possible_cpu(cpu) { |
| struct srcu_data *cpuc = per_cpu_ptr(sp->sda, cpu); |
| |
| sum += READ_ONCE(cpuc->srcu_unlock_count[idx]); |
| } |
| return sum; |
| } |
| |
| /* |
| * Return true if the number of pre-existing readers is determined to |
| * be zero. |
| */ |
| static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx) |
| { |
| unsigned long unlocks; |
| |
| unlocks = srcu_readers_unlock_idx(sp, idx); |
| |
| /* |
| * Make sure that a lock is always counted if the corresponding |
| * unlock is counted. Needs to be a smp_mb() as the read side may |
| * contain a read from a variable that is written to before the |
| * synchronize_srcu() in the write side. In this case smp_mb()s |
| * A and B act like the store buffering pattern. |
| * |
| * This smp_mb() also pairs with smp_mb() C to prevent accesses |
| * after the synchronize_srcu() from being executed before the |
| * grace period ends. |
| */ |
| smp_mb(); /* A */ |
| |
| /* |
| * If the locks are the same as the unlocks, then there must have |
| * been no readers on this index at some time in between. This does |
| * not mean that there are no more readers, as one could have read |
| * the current index but not have incremented the lock counter yet. |
| * |
| * Possible bug: There is no guarantee that there haven't been |
| * ULONG_MAX increments of ->srcu_lock_count[] since the unlocks were |
| * counted, meaning that this could return true even if there are |
| * still active readers. Since there are no memory barriers around |
| * srcu_flip(), the CPU is not required to increment ->srcu_idx |
| * before running srcu_readers_unlock_idx(), which means that there |
| * could be an arbitrarily large number of critical sections that |
| * execute after srcu_readers_unlock_idx() but use the old value |
| * of ->srcu_idx. |
| */ |
| return srcu_readers_lock_idx(sp, idx) == unlocks; |
| } |
| |
| /** |
| * srcu_readers_active - returns true if there are readers. and false |
| * otherwise |
| * @sp: which srcu_struct to count active readers (holding srcu_read_lock). |
| * |
| * Note that this is not an atomic primitive, and can therefore suffer |
| * severe errors when invoked on an active srcu_struct. That said, it |
| * can be useful as an error check at cleanup time. |
| */ |
| static bool srcu_readers_active(struct srcu_struct *sp) |
| { |
| int cpu; |
| unsigned long sum = 0; |
| |
| for_each_possible_cpu(cpu) { |
| struct srcu_data *cpuc = per_cpu_ptr(sp->sda, cpu); |
| |
| sum += READ_ONCE(cpuc->srcu_lock_count[0]); |
| sum += READ_ONCE(cpuc->srcu_lock_count[1]); |
| sum -= READ_ONCE(cpuc->srcu_unlock_count[0]); |
| sum -= READ_ONCE(cpuc->srcu_unlock_count[1]); |
| } |
| return sum; |
| } |
| |
| #define SRCU_INTERVAL 1 |
| |
| /* |
| * Return grace-period delay, zero if there are expedited grace |
| * periods pending, SRCU_INTERVAL otherwise. |
| */ |
| static unsigned long srcu_get_delay(struct srcu_struct *sp) |
| { |
| if (ULONG_CMP_LT(READ_ONCE(sp->srcu_gp_seq), |
| READ_ONCE(sp->srcu_gp_seq_needed_exp))) |
| return 0; |
| return SRCU_INTERVAL; |
| } |
| |
| /** |
| * cleanup_srcu_struct - deconstruct a sleep-RCU structure |
| * @sp: structure to clean up. |
| * |
| * Must invoke this after you are finished using a given srcu_struct that |
| * was initialized via init_srcu_struct(), else you leak memory. |
| */ |
| void cleanup_srcu_struct(struct srcu_struct *sp) |
| { |
| int cpu; |
| |
| if (WARN_ON(!srcu_get_delay(sp))) |
| return; /* Leakage unless caller handles error. */ |
| if (WARN_ON(srcu_readers_active(sp))) |
| return; /* Leakage unless caller handles error. */ |
| flush_delayed_work(&sp->work); |
| for_each_possible_cpu(cpu) |
| flush_delayed_work(&per_cpu_ptr(sp->sda, cpu)->work); |
| if (WARN_ON(rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) != SRCU_STATE_IDLE) || |
| WARN_ON(srcu_readers_active(sp))) { |
| pr_info("cleanup_srcu_struct: Active srcu_struct %p state: %d\n", sp, rcu_seq_state(READ_ONCE(sp->srcu_gp_seq))); |
| return; /* Caller forgot to stop doing call_srcu()? */ |
| } |
| free_percpu(sp->sda); |
| sp->sda = NULL; |
| } |
| EXPORT_SYMBOL_GPL(cleanup_srcu_struct); |
| |
| /* |
| * Counts the new reader in the appropriate per-CPU element of the |
| * srcu_struct. |
| * Returns an index that must be passed to the matching srcu_read_unlock(). |
| */ |
| int __srcu_read_lock(struct srcu_struct *sp) |
| { |
| int idx; |
| |
| idx = READ_ONCE(sp->srcu_idx) & 0x1; |
| this_cpu_inc(sp->sda->srcu_lock_count[idx]); |
| smp_mb(); /* B */ /* Avoid leaking the critical section. */ |
| return idx; |
| } |
| EXPORT_SYMBOL_GPL(__srcu_read_lock); |
| |
| /* |
| * Removes the count for the old reader from the appropriate per-CPU |
| * element of the srcu_struct. Note that this may well be a different |
| * CPU than that which was incremented by the corresponding srcu_read_lock(). |
| */ |
| void __srcu_read_unlock(struct srcu_struct *sp, int idx) |
| { |
| smp_mb(); /* C */ /* Avoid leaking the critical section. */ |
| this_cpu_inc(sp->sda->srcu_unlock_count[idx]); |
| } |
| EXPORT_SYMBOL_GPL(__srcu_read_unlock); |
| |
| /* |
| * We use an adaptive strategy for synchronize_srcu() and especially for |
| * synchronize_srcu_expedited(). We spin for a fixed time period |
| * (defined below) to allow SRCU readers to exit their read-side critical |
| * sections. If there are still some readers after a few microseconds, |
| * we repeatedly block for 1-millisecond time periods. |
| */ |
| #define SRCU_RETRY_CHECK_DELAY 5 |
| |
| /* |
| * Start an SRCU grace period. |
| */ |
| static void srcu_gp_start(struct srcu_struct *sp) |
| { |
| struct srcu_data *sdp = this_cpu_ptr(sp->sda); |
| int state; |
| |
| RCU_LOCKDEP_WARN(!lockdep_is_held(&sp->gp_lock), |
| "Invoked srcu_gp_start() without ->gp_lock!"); |
| WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)); |
| rcu_segcblist_advance(&sdp->srcu_cblist, |
| rcu_seq_current(&sp->srcu_gp_seq)); |
| (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, |
| rcu_seq_snap(&sp->srcu_gp_seq)); |
| smp_mb(); /* Order prior store to ->srcu_gp_seq_needed vs. GP start. */ |
| rcu_seq_start(&sp->srcu_gp_seq); |
| state = rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)); |
| WARN_ON_ONCE(state != SRCU_STATE_SCAN1); |
| } |
| |
| /* |
| * Track online CPUs to guide callback workqueue placement. |
| */ |
| DEFINE_PER_CPU(bool, srcu_online); |
| |
| void srcu_online_cpu(unsigned int cpu) |
| { |
| WRITE_ONCE(per_cpu(srcu_online, cpu), true); |
| } |
| |
| void srcu_offline_cpu(unsigned int cpu) |
| { |
| WRITE_ONCE(per_cpu(srcu_online, cpu), false); |
| } |
| |
| /* |
| * Place the workqueue handler on the specified CPU if online, otherwise |
| * just run it whereever. This is useful for placing workqueue handlers |
| * that are to invoke the specified CPU's callbacks. |
| */ |
| static bool srcu_queue_delayed_work_on(int cpu, struct workqueue_struct *wq, |
| struct delayed_work *dwork, |
| unsigned long delay) |
| { |
| bool ret; |
| |
| preempt_disable(); |
| if (READ_ONCE(per_cpu(srcu_online, cpu))) |
| ret = queue_delayed_work_on(cpu, wq, dwork, delay); |
| else |
| ret = queue_delayed_work(wq, dwork, delay); |
| preempt_enable(); |
| return ret; |
| } |
| |
| /* |
| * Schedule callback invocation for the specified srcu_data structure, |
| * if possible, on the corresponding CPU. |
| */ |
| static void srcu_schedule_cbs_sdp(struct srcu_data *sdp, unsigned long delay) |
| { |
| srcu_queue_delayed_work_on(sdp->cpu, system_power_efficient_wq, |
| &sdp->work, delay); |
| } |
| |
| /* |
| * Schedule callback invocation for all srcu_data structures associated |
| * with the specified srcu_node structure that have callbacks for the |
| * just-completed grace period, the one corresponding to idx. If possible, |
| * schedule this invocation on the corresponding CPUs. |
| */ |
| static void srcu_schedule_cbs_snp(struct srcu_struct *sp, struct srcu_node *snp, |
| unsigned long mask, unsigned long delay) |
| { |
| int cpu; |
| |
| for (cpu = snp->grplo; cpu <= snp->grphi; cpu++) { |
| if (!(mask & (1 << (cpu - snp->grplo)))) |
| continue; |
| srcu_schedule_cbs_sdp(per_cpu_ptr(sp->sda, cpu), delay); |
| } |
| } |
| |
| /* |
| * Note the end of an SRCU grace period. Initiates callback invocation |
| * and starts a new grace period if needed. |
| * |
| * The ->srcu_cb_mutex acquisition does not protect any data, but |
| * instead prevents more than one grace period from starting while we |
| * are initiating callback invocation. This allows the ->srcu_have_cbs[] |
| * array to have a finite number of elements. |
| */ |
| static void srcu_gp_end(struct srcu_struct *sp) |
| { |
| unsigned long cbdelay; |
| bool cbs; |
| unsigned long gpseq; |
| int idx; |
| int idxnext; |
| unsigned long mask; |
| struct srcu_node *snp; |
| |
| /* Prevent more than one additional grace period. */ |
| mutex_lock(&sp->srcu_cb_mutex); |
| |
| /* End the current grace period. */ |
| spin_lock_irq(&sp->gp_lock); |
| idx = rcu_seq_state(sp->srcu_gp_seq); |
| WARN_ON_ONCE(idx != SRCU_STATE_SCAN2); |
| cbdelay = srcu_get_delay(sp); |
| sp->srcu_last_gp_end = ktime_get_mono_fast_ns(); |
| rcu_seq_end(&sp->srcu_gp_seq); |
| gpseq = rcu_seq_current(&sp->srcu_gp_seq); |
| if (ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, gpseq)) |
| sp->srcu_gp_seq_needed_exp = gpseq; |
| spin_unlock_irq(&sp->gp_lock); |
| mutex_unlock(&sp->srcu_gp_mutex); |
| /* A new grace period can start at this point. But only one. */ |
| |
| /* Initiate callback invocation as needed. */ |
| idx = rcu_seq_ctr(gpseq) % ARRAY_SIZE(snp->srcu_have_cbs); |
| idxnext = (idx + 1) % ARRAY_SIZE(snp->srcu_have_cbs); |
| rcu_for_each_node_breadth_first(sp, snp) { |
| spin_lock_irq(&snp->lock); |
| cbs = false; |
| if (snp >= sp->level[rcu_num_lvls - 1]) |
| cbs = snp->srcu_have_cbs[idx] == gpseq; |
| snp->srcu_have_cbs[idx] = gpseq; |
| rcu_seq_set_state(&snp->srcu_have_cbs[idx], 1); |
| if (ULONG_CMP_LT(snp->srcu_gp_seq_needed_exp, gpseq)) |
| snp->srcu_gp_seq_needed_exp = gpseq; |
| mask = snp->srcu_data_have_cbs[idx]; |
| snp->srcu_data_have_cbs[idx] = 0; |
| spin_unlock_irq(&snp->lock); |
| if (cbs) { |
| smp_mb(); /* GP end before CB invocation. */ |
| srcu_schedule_cbs_snp(sp, snp, mask, cbdelay); |
| } |
| } |
| |
| /* Callback initiation done, allow grace periods after next. */ |
| mutex_unlock(&sp->srcu_cb_mutex); |
| |
| /* Start a new grace period if needed. */ |
| spin_lock_irq(&sp->gp_lock); |
| gpseq = rcu_seq_current(&sp->srcu_gp_seq); |
| if (!rcu_seq_state(gpseq) && |
| ULONG_CMP_LT(gpseq, sp->srcu_gp_seq_needed)) { |
| srcu_gp_start(sp); |
| spin_unlock_irq(&sp->gp_lock); |
| /* Throttle expedited grace periods: Should be rare! */ |
| srcu_reschedule(sp, rcu_seq_ctr(gpseq) & 0x3ff |
| ? 0 : SRCU_INTERVAL); |
| } else { |
| spin_unlock_irq(&sp->gp_lock); |
| } |
| } |
| |
| /* |
| * Funnel-locking scheme to scalably mediate many concurrent expedited |
| * grace-period requests. This function is invoked for the first known |
| * expedited request for a grace period that has already been requested, |
| * but without expediting. To start a completely new grace period, |
| * whether expedited or not, use srcu_funnel_gp_start() instead. |
| */ |
| static void srcu_funnel_exp_start(struct srcu_struct *sp, struct srcu_node *snp, |
| unsigned long s) |
| { |
| unsigned long flags; |
| |
| for (; snp != NULL; snp = snp->srcu_parent) { |
| if (rcu_seq_done(&sp->srcu_gp_seq, s) || |
| ULONG_CMP_GE(READ_ONCE(snp->srcu_gp_seq_needed_exp), s)) |
| return; |
| spin_lock_irqsave(&snp->lock, flags); |
| if (ULONG_CMP_GE(snp->srcu_gp_seq_needed_exp, s)) { |
| spin_unlock_irqrestore(&snp->lock, flags); |
| return; |
| } |
| WRITE_ONCE(snp->srcu_gp_seq_needed_exp, s); |
| spin_unlock_irqrestore(&snp->lock, flags); |
| } |
| spin_lock_irqsave(&sp->gp_lock, flags); |
| if (!ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s)) |
| sp->srcu_gp_seq_needed_exp = s; |
| spin_unlock_irqrestore(&sp->gp_lock, flags); |
| } |
| |
| /* |
| * Funnel-locking scheme to scalably mediate many concurrent grace-period |
| * requests. The winner has to do the work of actually starting grace |
| * period s. Losers must either ensure that their desired grace-period |
| * number is recorded on at least their leaf srcu_node structure, or they |
| * must take steps to invoke their own callbacks. |
| */ |
| static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, |
| unsigned long s, bool do_norm) |
| { |
| unsigned long flags; |
| int idx = rcu_seq_ctr(s) % ARRAY_SIZE(sdp->mynode->srcu_have_cbs); |
| struct srcu_node *snp = sdp->mynode; |
| unsigned long snp_seq; |
| |
| /* Each pass through the loop does one level of the srcu_node tree. */ |
| for (; snp != NULL; snp = snp->srcu_parent) { |
| if (rcu_seq_done(&sp->srcu_gp_seq, s) && snp != sdp->mynode) |
| return; /* GP already done and CBs recorded. */ |
| spin_lock_irqsave(&snp->lock, flags); |
| if (ULONG_CMP_GE(snp->srcu_have_cbs[idx], s)) { |
| snp_seq = snp->srcu_have_cbs[idx]; |
| if (snp == sdp->mynode && snp_seq == s) |
| snp->srcu_data_have_cbs[idx] |= sdp->grpmask; |
| spin_unlock_irqrestore(&snp->lock, flags); |
| if (snp == sdp->mynode && snp_seq != s) { |
| smp_mb(); /* CBs after GP! */ |
| srcu_schedule_cbs_sdp(sdp, do_norm |
| ? SRCU_INTERVAL |
| : 0); |
| return; |
| } |
| if (!do_norm) |
| srcu_funnel_exp_start(sp, snp, s); |
| return; |
| } |
| snp->srcu_have_cbs[idx] = s; |
| if (snp == sdp->mynode) |
| snp->srcu_data_have_cbs[idx] |= sdp->grpmask; |
| if (!do_norm && ULONG_CMP_LT(snp->srcu_gp_seq_needed_exp, s)) |
| snp->srcu_gp_seq_needed_exp = s; |
| spin_unlock_irqrestore(&snp->lock, flags); |
| } |
| |
| /* Top of tree, must ensure the grace period will be started. */ |
| spin_lock_irqsave(&sp->gp_lock, flags); |
| if (ULONG_CMP_LT(sp->srcu_gp_seq_needed, s)) { |
| /* |
| * Record need for grace period s. Pair with load |
| * acquire setting up for initialization. |
| */ |
| smp_store_release(&sp->srcu_gp_seq_needed, s); /*^^^*/ |
| } |
| if (!do_norm && ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s)) |
| sp->srcu_gp_seq_needed_exp = s; |
| |
| /* If grace period not already done and none in progress, start it. */ |
| if (!rcu_seq_done(&sp->srcu_gp_seq, s) && |
| rcu_seq_state(sp->srcu_gp_seq) == SRCU_STATE_IDLE) { |
| WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)); |
| srcu_gp_start(sp); |
| queue_delayed_work(system_power_efficient_wq, &sp->work, |
| srcu_get_delay(sp)); |
| } |
| spin_unlock_irqrestore(&sp->gp_lock, flags); |
| } |
| |
| /* |
| * Wait until all readers counted by array index idx complete, but |
| * loop an additional time if there is an expedited grace period pending. |
| * The caller must ensure that ->srcu_idx is not changed while checking. |
| */ |
| static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount) |
| { |
| for (;;) { |
| if (srcu_readers_active_idx_check(sp, idx)) |
| return true; |
| if (--trycount + !srcu_get_delay(sp) <= 0) |
| return false; |
| udelay(SRCU_RETRY_CHECK_DELAY); |
| } |
| } |
| |
| /* |
| * Increment the ->srcu_idx counter so that future SRCU readers will |
| * use the other rank of the ->srcu_(un)lock_count[] arrays. This allows |
| * us to wait for pre-existing readers in a starvation-free manner. |
| */ |
| static void srcu_flip(struct srcu_struct *sp) |
| { |
| WRITE_ONCE(sp->srcu_idx, sp->srcu_idx + 1); |
| |
| /* |
| * Ensure that if the updater misses an __srcu_read_unlock() |
| * increment, that task's next __srcu_read_lock() will see the |
| * above counter update. Note that both this memory barrier |
| * and the one in srcu_readers_active_idx_check() provide the |
| * guarantee for __srcu_read_lock(). |
| */ |
| smp_mb(); /* D */ /* Pairs with C. */ |
| } |
| |
| /* |
| * If SRCU is likely idle, return true, otherwise return false. |
| * |
| * Note that it is OK for several current from-idle requests for a new |
| * grace period from idle to specify expediting because they will all end |
| * up requesting the same grace period anyhow. So no loss. |
| * |
| * Note also that if any CPU (including the current one) is still invoking |
| * callbacks, this function will nevertheless say "idle". This is not |
| * ideal, but the overhead of checking all CPUs' callback lists is even |
| * less ideal, especially on large systems. Furthermore, the wakeup |
| * can happen before the callback is fully removed, so we have no choice |
| * but to accept this type of error. |
| * |
| * This function is also subject to counter-wrap errors, but let's face |
| * it, if this function was preempted for enough time for the counters |
| * to wrap, it really doesn't matter whether or not we expedite the grace |
| * period. The extra overhead of a needlessly expedited grace period is |
| * negligible when amoritized over that time period, and the extra latency |
| * of a needlessly non-expedited grace period is similarly negligible. |
| */ |
| static bool srcu_might_be_idle(struct srcu_struct *sp) |
| { |
| unsigned long curseq; |
| unsigned long flags; |
| struct srcu_data *sdp; |
| unsigned long t; |
| |
| /* If the local srcu_data structure has callbacks, not idle. */ |
| local_irq_save(flags); |
| sdp = this_cpu_ptr(sp->sda); |
| if (rcu_segcblist_pend_cbs(&sdp->srcu_cblist)) { |
| local_irq_restore(flags); |
| return false; /* Callbacks already present, so not idle. */ |
| } |
| local_irq_restore(flags); |
| |
| /* |
| * No local callbacks, so probabalistically probe global state. |
| * Exact information would require acquiring locks, which would |
| * kill scalability, hence the probabalistic nature of the probe. |
| */ |
| |
| /* First, see if enough time has passed since the last GP. */ |
| t = ktime_get_mono_fast_ns(); |
| if (exp_holdoff == 0 || |
| time_in_range_open(t, sp->srcu_last_gp_end, |
| sp->srcu_last_gp_end + exp_holdoff)) |
| return false; /* Too soon after last GP. */ |
| |
| /* Next, check for probable idleness. */ |
| curseq = rcu_seq_current(&sp->srcu_gp_seq); |
| smp_mb(); /* Order ->srcu_gp_seq with ->srcu_gp_seq_needed. */ |
| if (ULONG_CMP_LT(curseq, READ_ONCE(sp->srcu_gp_seq_needed))) |
| return false; /* Grace period in progress, so not idle. */ |
| smp_mb(); /* Order ->srcu_gp_seq with prior access. */ |
| if (curseq != rcu_seq_current(&sp->srcu_gp_seq)) |
| return false; /* GP # changed, so not idle. */ |
| return true; /* With reasonable probability, idle! */ |
| } |
| |
| /* |
| * Enqueue an SRCU callback on the srcu_data structure associated with |
| * the current CPU and the specified srcu_struct structure, initiating |
| * grace-period processing if it is not already running. |
| * |
| * Note that all CPUs must agree that the grace period extended beyond |
| * all pre-existing SRCU read-side critical section. On systems with |
| * more than one CPU, this means that when "func()" is invoked, each CPU |
| * is guaranteed to have executed a full memory barrier since the end of |
| * its last corresponding SRCU read-side critical section whose beginning |
| * preceded the call to call_rcu(). It also means that each CPU executing |
| * an SRCU read-side critical section that continues beyond the start of |
| * "func()" must have executed a memory barrier after the call_rcu() |
| * but before the beginning of that SRCU read-side critical section. |
| * Note that these guarantees include CPUs that are offline, idle, or |
| * executing in user mode, as well as CPUs that are executing in the kernel. |
| * |
| * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the |
| * resulting SRCU callback function "func()", then both CPU A and CPU |
| * B are guaranteed to execute a full memory barrier during the time |
| * interval between the call to call_rcu() and the invocation of "func()". |
| * This guarantee applies even if CPU A and CPU B are the same CPU (but |
| * again only if the system has more than one CPU). |
| * |
| * Of course, these guarantees apply only for invocations of call_srcu(), |
| * srcu_read_lock(), and srcu_read_unlock() that are all passed the same |
| * srcu_struct structure. |
| */ |
| void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, |
| rcu_callback_t func, bool do_norm) |
| { |
| unsigned long flags; |
| bool needexp = false; |
| bool needgp = false; |
| unsigned long s; |
| struct srcu_data *sdp; |
| |
| check_init_srcu_struct(sp); |
| rhp->func = func; |
| local_irq_save(flags); |
| sdp = this_cpu_ptr(sp->sda); |
| spin_lock(&sdp->lock); |
| rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp, false); |
| rcu_segcblist_advance(&sdp->srcu_cblist, |
| rcu_seq_current(&sp->srcu_gp_seq)); |
| s = rcu_seq_snap(&sp->srcu_gp_seq); |
| (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, s); |
| if (ULONG_CMP_LT(sdp->srcu_gp_seq_needed, s)) { |
| sdp->srcu_gp_seq_needed = s; |
| needgp = true; |
| } |
| if (!do_norm && ULONG_CMP_LT(sdp->srcu_gp_seq_needed_exp, s)) { |
| sdp->srcu_gp_seq_needed_exp = s; |
| needexp = true; |
| } |
| spin_unlock_irqrestore(&sdp->lock, flags); |
| if (needgp) |
| srcu_funnel_gp_start(sp, sdp, s, do_norm); |
| else if (needexp) |
| srcu_funnel_exp_start(sp, sdp->mynode, s); |
| } |
| |
| void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, |
| rcu_callback_t func) |
| { |
| __call_srcu(sp, rhp, func, true); |
| } |
| EXPORT_SYMBOL_GPL(call_srcu); |
| |
| /* |
| * Helper function for synchronize_srcu() and synchronize_srcu_expedited(). |
| */ |
| static void __synchronize_srcu(struct srcu_struct *sp, bool do_norm) |
| { |
| struct rcu_synchronize rcu; |
| |
| RCU_LOCKDEP_WARN(lock_is_held(&sp->dep_map) || |
| lock_is_held(&rcu_bh_lock_map) || |
| lock_is_held(&rcu_lock_map) || |
| lock_is_held(&rcu_sched_lock_map), |
| "Illegal synchronize_srcu() in same-type SRCU (or in RCU) read-side critical section"); |
| |
| if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) |
| return; |
| might_sleep(); |
| check_init_srcu_struct(sp); |
| init_completion(&rcu.completion); |
| init_rcu_head_on_stack(&rcu.head); |
| __call_srcu(sp, &rcu.head, wakeme_after_rcu, do_norm); |
| wait_for_completion(&rcu.completion); |
| destroy_rcu_head_on_stack(&rcu.head); |
| } |
| |
| /** |
| * synchronize_srcu_expedited - Brute-force SRCU grace period |
| * @sp: srcu_struct with which to synchronize. |
| * |
| * Wait for an SRCU grace period to elapse, but be more aggressive about |
| * spinning rather than blocking when waiting. |
| * |
| * Note that synchronize_srcu_expedited() has the same deadlock and |
| * memory-ordering properties as does synchronize_srcu(). |
| */ |
| void synchronize_srcu_expedited(struct srcu_struct *sp) |
| { |
| __synchronize_srcu(sp, rcu_gp_is_normal()); |
| } |
| EXPORT_SYMBOL_GPL(synchronize_srcu_expedited); |
| |
| /** |
| * synchronize_srcu - wait for prior SRCU read-side critical-section completion |
| * @sp: srcu_struct with which to synchronize. |
| * |
| * Wait for the count to drain to zero of both indexes. To avoid the |
| * possible starvation of synchronize_srcu(), it waits for the count of |
| * the index=((->srcu_idx & 1) ^ 1) to drain to zero at first, |
| * and then flip the srcu_idx and wait for the count of the other index. |
| * |
| * Can block; must be called from process context. |
| * |
| * Note that it is illegal to call synchronize_srcu() from the corresponding |
| * SRCU read-side critical section; doing so will result in deadlock. |
| * However, it is perfectly legal to call synchronize_srcu() on one |
| * srcu_struct from some other srcu_struct's read-side critical section, |
| * as long as the resulting graph of srcu_structs is acyclic. |
| * |
| * There are memory-ordering constraints implied by synchronize_srcu(). |
| * On systems with more than one CPU, when synchronize_srcu() returns, |
| * each CPU is guaranteed to have executed a full memory barrier since |
| * the end of its last corresponding SRCU-sched read-side critical section |
| * whose beginning preceded the call to synchronize_srcu(). In addition, |
| * each CPU having an SRCU read-side critical section that extends beyond |
| * the return from synchronize_srcu() is guaranteed to have executed a |
| * full memory barrier after the beginning of synchronize_srcu() and before |
| * the beginning of that SRCU read-side critical section. Note that these |
| * guarantees include CPUs that are offline, idle, or executing in user mode, |
| * as well as CPUs that are executing in the kernel. |
| * |
| * Furthermore, if CPU A invoked synchronize_srcu(), which returned |
| * to its caller on CPU B, then both CPU A and CPU B are guaranteed |
| * to have executed a full memory barrier during the execution of |
| * synchronize_srcu(). This guarantee applies even if CPU A and CPU B |
| * are the same CPU, but again only if the system has more than one CPU. |
| * |
| * Of course, these memory-ordering guarantees apply only when |
| * synchronize_srcu(), srcu_read_lock(), and srcu_read_unlock() are |
| * passed the same srcu_struct structure. |
| * |
| * If SRCU is likely idle, expedite the first request. This semantic |
| * was provided by Classic SRCU, and is relied upon by its users, so TREE |
| * SRCU must also provide it. Note that detecting idleness is heuristic |
| * and subject to both false positives and negatives. |
| */ |
| void synchronize_srcu(struct srcu_struct *sp) |
| { |
| if (srcu_might_be_idle(sp) || rcu_gp_is_expedited()) |
| synchronize_srcu_expedited(sp); |
| else |
| __synchronize_srcu(sp, true); |
| } |
| EXPORT_SYMBOL_GPL(synchronize_srcu); |
| |
| /* |
| * Callback function for srcu_barrier() use. |
| */ |
| static void srcu_barrier_cb(struct rcu_head *rhp) |
| { |
| struct srcu_data *sdp; |
| struct srcu_struct *sp; |
| |
| sdp = container_of(rhp, struct srcu_data, srcu_barrier_head); |
| sp = sdp->sp; |
| if (atomic_dec_and_test(&sp->srcu_barrier_cpu_cnt)) |
| complete(&sp->srcu_barrier_completion); |
| } |
| |
| /** |
| * srcu_barrier - Wait until all in-flight call_srcu() callbacks complete. |
| * @sp: srcu_struct on which to wait for in-flight callbacks. |
| */ |
| void srcu_barrier(struct srcu_struct *sp) |
| { |
| int cpu; |
| struct srcu_data *sdp; |
| unsigned long s = rcu_seq_snap(&sp->srcu_barrier_seq); |
| |
| check_init_srcu_struct(sp); |
| mutex_lock(&sp->srcu_barrier_mutex); |
| if (rcu_seq_done(&sp->srcu_barrier_seq, s)) { |
| smp_mb(); /* Force ordering following return. */ |
| mutex_unlock(&sp->srcu_barrier_mutex); |
| return; /* Someone else did our work for us. */ |
| } |
| rcu_seq_start(&sp->srcu_barrier_seq); |
| init_completion(&sp->srcu_barrier_completion); |
| |
| /* Initial count prevents reaching zero until all CBs are posted. */ |
| atomic_set(&sp->srcu_barrier_cpu_cnt, 1); |
| |
| /* |
| * Each pass through this loop enqueues a callback, but only |
| * on CPUs already having callbacks enqueued. Note that if |
| * a CPU already has callbacks enqueue, it must have already |
| * registered the need for a future grace period, so all we |
| * need do is enqueue a callback that will use the same |
| * grace period as the last callback already in the queue. |
| */ |
| for_each_possible_cpu(cpu) { |
| sdp = per_cpu_ptr(sp->sda, cpu); |
| spin_lock_irq(&sdp->lock); |
| atomic_inc(&sp->srcu_barrier_cpu_cnt); |
| sdp->srcu_barrier_head.func = srcu_barrier_cb; |
| if (!rcu_segcblist_entrain(&sdp->srcu_cblist, |
| &sdp->srcu_barrier_head, 0)) |
| atomic_dec(&sp->srcu_barrier_cpu_cnt); |
| spin_unlock_irq(&sdp->lock); |
| } |
| |
| /* Remove the initial count, at which point reaching zero can happen. */ |
| if (atomic_dec_and_test(&sp->srcu_barrier_cpu_cnt)) |
| complete(&sp->srcu_barrier_completion); |
| wait_for_completion(&sp->srcu_barrier_completion); |
| |
| rcu_seq_end(&sp->srcu_barrier_seq); |
| mutex_unlock(&sp->srcu_barrier_mutex); |
| } |
| EXPORT_SYMBOL_GPL(srcu_barrier); |
| |
| /** |
| * srcu_batches_completed - return batches completed. |
| * @sp: srcu_struct on which to report batch completion. |
| * |
| * Report the number of batches, correlated with, but not necessarily |
| * precisely the same as, the number of grace periods that have elapsed. |
| */ |
| unsigned long srcu_batches_completed(struct srcu_struct *sp) |
| { |
| return sp->srcu_idx; |
| } |
| EXPORT_SYMBOL_GPL(srcu_batches_completed); |
| |
| /* |
| * Core SRCU state machine. Push state bits of ->srcu_gp_seq |
| * to SRCU_STATE_SCAN2, and invoke srcu_gp_end() when scan has |
| * completed in that state. |
| */ |
| static void srcu_advance_state(struct srcu_struct *sp) |
| { |
| int idx; |
| |
| mutex_lock(&sp->srcu_gp_mutex); |
| |
| /* |
| * Because readers might be delayed for an extended period after |
| * fetching ->srcu_idx for their index, at any point in time there |
| * might well be readers using both idx=0 and idx=1. We therefore |
| * need to wait for readers to clear from both index values before |
| * invoking a callback. |
| * |
| * The load-acquire ensures that we see the accesses performed |
| * by the prior grace period. |
| */ |
| idx = rcu_seq_state(smp_load_acquire(&sp->srcu_gp_seq)); /* ^^^ */ |
| if (idx == SRCU_STATE_IDLE) { |
| spin_lock_irq(&sp->gp_lock); |
| if (ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)) { |
| WARN_ON_ONCE(rcu_seq_state(sp->srcu_gp_seq)); |
| spin_unlock_irq(&sp->gp_lock); |
| mutex_unlock(&sp->srcu_gp_mutex); |
| return; |
| } |
| idx = rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)); |
| if (idx == SRCU_STATE_IDLE) |
| srcu_gp_start(sp); |
| spin_unlock_irq(&sp->gp_lock); |
| if (idx != SRCU_STATE_IDLE) { |
| mutex_unlock(&sp->srcu_gp_mutex); |
| return; /* Someone else started the grace period. */ |
| } |
| } |
| |
| if (rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) == SRCU_STATE_SCAN1) { |
| idx = 1 ^ (sp->srcu_idx & 1); |
| if (!try_check_zero(sp, idx, 1)) { |
| mutex_unlock(&sp->srcu_gp_mutex); |
| return; /* readers present, retry later. */ |
| } |
| srcu_flip(sp); |
| rcu_seq_set_state(&sp->srcu_gp_seq, SRCU_STATE_SCAN2); |
| } |
| |
| if (rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) == SRCU_STATE_SCAN2) { |
| |
| /* |
| * SRCU read-side critical sections are normally short, |
| * so check at least twice in quick succession after a flip. |
| */ |
| idx = 1 ^ (sp->srcu_idx & 1); |
| if (!try_check_zero(sp, idx, 2)) { |
| mutex_unlock(&sp->srcu_gp_mutex); |
| return; /* readers present, retry later. */ |
| } |
| srcu_gp_end(sp); /* Releases ->srcu_gp_mutex. */ |
| } |
| } |
| |
| /* |
| * Invoke a limited number of SRCU callbacks that have passed through |
| * their grace period. If there are more to do, SRCU will reschedule |
| * the workqueue. Note that needed memory barriers have been executed |
| * in this task's context by srcu_readers_active_idx_check(). |
| */ |
| static void srcu_invoke_callbacks(struct work_struct *work) |
| { |
| bool more; |
| struct rcu_cblist ready_cbs; |
| struct rcu_head *rhp; |
| struct srcu_data *sdp; |
| struct srcu_struct *sp; |
| |
| sdp = container_of(work, struct srcu_data, work.work); |
| sp = sdp->sp; |
| rcu_cblist_init(&ready_cbs); |
| spin_lock_irq(&sdp->lock); |
| smp_mb(); /* Old grace periods before callback invocation! */ |
| rcu_segcblist_advance(&sdp->srcu_cblist, |
| rcu_seq_current(&sp->srcu_gp_seq)); |
| if (sdp->srcu_cblist_invoking || |
| !rcu_segcblist_ready_cbs(&sdp->srcu_cblist)) { |
| spin_unlock_irq(&sdp->lock); |
| return; /* Someone else on the job or nothing to do. */ |
| } |
| |
| /* We are on the job! Extract and invoke ready callbacks. */ |
| sdp->srcu_cblist_invoking = true; |
| rcu_segcblist_extract_done_cbs(&sdp->srcu_cblist, &ready_cbs); |
| spin_unlock_irq(&sdp->lock); |
| rhp = rcu_cblist_dequeue(&ready_cbs); |
| for (; rhp != NULL; rhp = rcu_cblist_dequeue(&ready_cbs)) { |
| local_bh_disable(); |
| rhp->func(rhp); |
| local_bh_enable(); |
| } |
| |
| /* |
| * Update counts, accelerate new callbacks, and if needed, |
| * schedule another round of callback invocation. |
| */ |
| spin_lock_irq(&sdp->lock); |
| rcu_segcblist_insert_count(&sdp->srcu_cblist, &ready_cbs); |
| (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, |
| rcu_seq_snap(&sp->srcu_gp_seq)); |
| sdp->srcu_cblist_invoking = false; |
| more = rcu_segcblist_ready_cbs(&sdp->srcu_cblist); |
| spin_unlock_irq(&sdp->lock); |
| if (more) |
| srcu_schedule_cbs_sdp(sdp, 0); |
| } |
| |
| /* |
| * Finished one round of SRCU grace period. Start another if there are |
| * more SRCU callbacks queued, otherwise put SRCU into not-running state. |
| */ |
| static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay) |
| { |
| bool pushgp = true; |
| |
| spin_lock_irq(&sp->gp_lock); |
| if (ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)) { |
| if (!WARN_ON_ONCE(rcu_seq_state(sp->srcu_gp_seq))) { |
| /* All requests fulfilled, time to go idle. */ |
| pushgp = false; |
| } |
| } else if (!rcu_seq_state(sp->srcu_gp_seq)) { |
| /* Outstanding request and no GP. Start one. */ |
| srcu_gp_start(sp); |
| } |
| spin_unlock_irq(&sp->gp_lock); |
| |
| if (pushgp) |
| queue_delayed_work(system_power_efficient_wq, &sp->work, delay); |
| } |
| |
| /* |
| * This is the work-queue function that handles SRCU grace periods. |
| */ |
| void process_srcu(struct work_struct *work) |
| { |
| struct srcu_struct *sp; |
| |
| sp = container_of(work, struct srcu_struct, work.work); |
| |
| srcu_advance_state(sp); |
| srcu_reschedule(sp, srcu_get_delay(sp)); |
| } |
| EXPORT_SYMBOL_GPL(process_srcu); |
| |
| void srcutorture_get_gp_data(enum rcutorture_type test_type, |
| struct srcu_struct *sp, int *flags, |
| unsigned long *gpnum, unsigned long *completed) |
| { |
| if (test_type != SRCU_FLAVOR) |
| return; |
| *flags = 0; |
| *completed = rcu_seq_ctr(sp->srcu_gp_seq); |
| *gpnum = rcu_seq_ctr(sp->srcu_gp_seq_needed); |
| } |
| EXPORT_SYMBOL_GPL(srcutorture_get_gp_data); |