Lines Matching +full:foo +full:- +full:queue
1 // SPDX-License-Identifier: GPL-2.0-only
3 * RT-Mutexes: simple blocking mutual exclusion locks with PI support
7 * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
8 * Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
17 * See Documentation/locking/rt-mutex-design.rst for details.
66 * lock->owner state tracking:
68 * lock->owner holds the task_struct pointer of the owner. Bit 0
79 * possible when bit 0 of lock->owner is 0.
82 * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock,
100 WRITE_ONCE(lock->owner, (struct task_struct *)val); in rt_mutex_set_owner()
105 lock->owner = (struct task_struct *) in clear_rt_mutex_waiters()
106 ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS); in clear_rt_mutex_waiters()
111 unsigned long owner, *p = (unsigned long *) &lock->owner; in fixup_rt_mutex_waiters()
118 * lock->owner still has the waiters bit set, otherwise the in fixup_rt_mutex_waiters()
122 * l->owner=T1 in fixup_rt_mutex_waiters()
124 * lock(l->lock) in fixup_rt_mutex_waiters()
125 * l->owner = T1 | HAS_WAITERS; in fixup_rt_mutex_waiters()
128 * unlock(l->lock) in fixup_rt_mutex_waiters()
132 * lock(l->lock) in fixup_rt_mutex_waiters()
133 * l->owner = T1 | HAS_WAITERS; in fixup_rt_mutex_waiters()
136 * unlock(l->lock) in fixup_rt_mutex_waiters()
138 * signal(->T2) signal(->T3) in fixup_rt_mutex_waiters()
139 * lock(l->lock) in fixup_rt_mutex_waiters()
142 * unlock(l->lock) in fixup_rt_mutex_waiters()
143 * lock(l->lock) in fixup_rt_mutex_waiters()
147 * unlock(l->lock) in fixup_rt_mutex_waiters()
148 * lock(l->lock) in fixup_rt_mutex_waiters()
151 * l->owner = owner in fixup_rt_mutex_waiters()
152 * owner = l->owner & ~HAS_WAITERS; in fixup_rt_mutex_waiters()
153 * ==> l->owner = T1 in fixup_rt_mutex_waiters()
155 * lock(l->lock) in fixup_rt_mutex_waiters()
158 * owner = l->owner & ~HAS_WAITERS; in fixup_rt_mutex_waiters()
159 * cmpxchg(l->owner, T1, NULL) in fixup_rt_mutex_waiters()
160 * ===> Success (l->owner = NULL) in fixup_rt_mutex_waiters()
162 * l->owner = owner in fixup_rt_mutex_waiters()
163 * ==> l->owner = T1 in fixup_rt_mutex_waiters()
168 * serialized by l->lock, so nothing else can modify the waiters in fixup_rt_mutex_waiters()
169 * bit. If the bit is set then nothing can change l->owner either in fixup_rt_mutex_waiters()
188 return try_cmpxchg_acquire(&lock->owner, &old, new); in rt_mutex_cmpxchg_acquire()
195 return try_cmpxchg_release(&lock->owner, &old, new); in rt_mutex_cmpxchg_release()
199 * Callers must hold the ->wait_lock -- which is the whole purpose as we force
205 unsigned long owner, *p = (unsigned long *) &lock->owner; in mark_rt_mutex_waiters()
216 * 2) Drop lock->wait_lock
221 __releases(lock->wait_lock) in unlock_rt_mutex_safe()
226 raw_spin_unlock_irqrestore(&lock->wait_lock, flags); in unlock_rt_mutex_safe()
272 lock->owner = (struct task_struct *) in mark_rt_mutex_waiters()
273 ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS); in mark_rt_mutex_waiters()
277 * Simple slow path only version: lock->owner is protected by lock->wait_lock.
281 __releases(lock->wait_lock) in unlock_rt_mutex_safe()
283 lock->owner = NULL; in unlock_rt_mutex_safe()
284 raw_spin_unlock_irqrestore(&lock->wait_lock, flags); in unlock_rt_mutex_safe()
291 int prio = task->prio; in __waiter_prio()
302 waiter->prio = __waiter_prio(task); in waiter_update_prio()
303 waiter->deadline = task->dl.deadline; in waiter_update_prio()
310 &(struct rt_mutex_waiter){ .prio = __waiter_prio(p), .deadline = (p)->dl.deadline }
315 if (left->prio < right->prio) in rt_mutex_waiter_less()
324 if (dl_prio(left->prio)) in rt_mutex_waiter_less()
325 return dl_time_before(left->deadline, right->deadline); in rt_mutex_waiter_less()
333 if (left->prio != right->prio) in rt_mutex_waiter_equal()
342 if (dl_prio(left->prio)) in rt_mutex_waiter_equal()
343 return left->deadline == right->deadline; in rt_mutex_waiter_equal()
359 if (rt_prio(waiter->prio) || dl_prio(waiter->prio)) in rt_mutex_steal()
385 /* NOTE: relies on waiter->ww_ctx being set before insertion */ in __waiter_less()
386 if (aw->ww_ctx) { in __waiter_less()
387 if (!bw->ww_ctx) in __waiter_less()
390 return (signed long)(aw->ww_ctx->stamp - in __waiter_less()
391 bw->ww_ctx->stamp) < 0; in __waiter_less()
400 rb_add_cached(&waiter->tree_entry, &lock->waiters, __waiter_less); in rt_mutex_enqueue()
406 if (RB_EMPTY_NODE(&waiter->tree_entry)) in rt_mutex_dequeue()
409 rb_erase_cached(&waiter->tree_entry, &lock->waiters); in rt_mutex_dequeue()
410 RB_CLEAR_NODE(&waiter->tree_entry); in rt_mutex_dequeue()
425 rb_add_cached(&waiter->pi_tree_entry, &task->pi_waiters, __pi_waiter_less); in rt_mutex_enqueue_pi()
431 if (RB_EMPTY_NODE(&waiter->pi_tree_entry)) in rt_mutex_dequeue_pi()
434 rb_erase_cached(&waiter->pi_tree_entry, &task->pi_waiters); in rt_mutex_dequeue_pi()
435 RB_CLEAR_NODE(&waiter->pi_tree_entry); in rt_mutex_dequeue_pi()
442 lockdep_assert_held(&p->pi_lock); in rt_mutex_adjust_prio()
445 pi_task = task_top_pi_waiter(p)->task; in rt_mutex_adjust_prio()
457 WARN_ON_ONCE(wqh->rtlock_task); in rt_mutex_wake_q_add_task()
459 wqh->rtlock_task = task; in rt_mutex_wake_q_add_task()
461 wake_q_add(&wqh->head, task); in rt_mutex_wake_q_add_task()
468 rt_mutex_wake_q_add_task(wqh, w->task, w->wake_state); in rt_mutex_wake_q_add()
473 if (IS_ENABLED(CONFIG_PREEMPT_RT) && wqh->rtlock_task) { in rt_mutex_wake_up_q()
474 wake_up_state(wqh->rtlock_task, TASK_RTLOCK_WAIT); in rt_mutex_wake_up_q()
475 put_task_struct(wqh->rtlock_task); in rt_mutex_wake_up_q()
476 wqh->rtlock_task = NULL; in rt_mutex_wake_up_q()
479 if (!wake_q_empty(&wqh->head)) in rt_mutex_wake_up_q()
480 wake_up_q(&wqh->head); in rt_mutex_wake_up_q()
510 return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL; in task_blocked_on_lock()
515 * Decreases task's usage by one - may thus free the task.
532 * Returns 0 or -EDEADLK.
537 * [P] task->pi_lock held
538 * [L] rtmutex->wait_lock held
554 * [1] lock(task->pi_lock); [R] acquire [P]
555 * [2] waiter = task->pi_blocked_on; [P]
557 * [4] lock = waiter->lock; [P]
558 * [5] if (!try_lock(lock->wait_lock)) { [P] try to acquire [L]
559 * unlock(task->pi_lock); release [P]
564 * [8] unlock(task->pi_lock); release [P]
569 * lock(task->pi_lock); [L] acquire [P]
572 * [13] unlock(task->pi_lock); release [P]
573 * unlock(lock->wait_lock); release [L]
613 top_task->comm, task_pid_nr(top_task)); in rt_mutex_adjust_prio_chain()
617 return -EDEADLK; in rt_mutex_adjust_prio_chain()
630 raw_spin_lock_irq(&task->pi_lock); in rt_mutex_adjust_prio_chain()
635 waiter = task->pi_blocked_on; in rt_mutex_adjust_prio_chain()
638 * [3] check_exit_conditions_1() protected by task->pi_lock. in rt_mutex_adjust_prio_chain()
665 if (next_lock != waiter->lock) in rt_mutex_adjust_prio_chain()
676 * P3 should not return -EDEADLK because it gets trapped in the cycle in rt_mutex_adjust_prio_chain()
677 * created by P1 and P2 (which will resolve -- and runs into in rt_mutex_adjust_prio_chain()
690 if (IS_ENABLED(CONFIG_PREEMPT_RT) && waiter->ww_ctx && detect_deadlock) in rt_mutex_adjust_prio_chain()
732 lock = waiter->lock; in rt_mutex_adjust_prio_chain()
734 * [5] We need to trylock here as we are holding task->pi_lock, in rt_mutex_adjust_prio_chain()
738 if (!raw_spin_trylock(&lock->wait_lock)) { in rt_mutex_adjust_prio_chain()
739 raw_spin_unlock_irq(&task->pi_lock); in rt_mutex_adjust_prio_chain()
745 * [6] check_exit_conditions_2() protected by task->pi_lock and in rt_mutex_adjust_prio_chain()
746 * lock->wait_lock. in rt_mutex_adjust_prio_chain()
754 ret = -EDEADLK; in rt_mutex_adjust_prio_chain()
759 * logic pick which of the contending threads gets -EDEADLK. in rt_mutex_adjust_prio_chain()
765 if (IS_ENABLED(CONFIG_PREEMPT_RT) && orig_waiter && orig_waiter->ww_ctx) in rt_mutex_adjust_prio_chain()
768 raw_spin_unlock(&lock->wait_lock); in rt_mutex_adjust_prio_chain()
782 raw_spin_unlock(&task->pi_lock); in rt_mutex_adjust_prio_chain()
786 * [9] check_exit_conditions_3 protected by lock->wait_lock. in rt_mutex_adjust_prio_chain()
790 raw_spin_unlock_irq(&lock->wait_lock); in rt_mutex_adjust_prio_chain()
796 raw_spin_lock(&task->pi_lock); in rt_mutex_adjust_prio_chain()
811 raw_spin_unlock(&task->pi_lock); in rt_mutex_adjust_prio_chain()
812 raw_spin_unlock_irq(&lock->wait_lock); in rt_mutex_adjust_prio_chain()
851 raw_spin_unlock(&task->pi_lock); in rt_mutex_adjust_prio_chain()
855 * [9] check_exit_conditions_3 protected by lock->wait_lock. in rt_mutex_adjust_prio_chain()
868 wake_up_state(waiter->task, waiter->wake_state); in rt_mutex_adjust_prio_chain()
869 raw_spin_unlock_irq(&lock->wait_lock); in rt_mutex_adjust_prio_chain()
875 raw_spin_lock(&task->pi_lock); in rt_mutex_adjust_prio_chain()
912 * [12] check_exit_conditions_4() protected by task->pi_lock in rt_mutex_adjust_prio_chain()
913 * and lock->wait_lock. The actual decisions are made after we in rt_mutex_adjust_prio_chain()
919 * task->pi_lock next_lock cannot be dereferenced anymore. in rt_mutex_adjust_prio_chain()
929 raw_spin_unlock(&task->pi_lock); in rt_mutex_adjust_prio_chain()
930 raw_spin_unlock_irq(&lock->wait_lock); in rt_mutex_adjust_prio_chain()
953 raw_spin_unlock_irq(&task->pi_lock); in rt_mutex_adjust_prio_chain()
961 * Try to take an rt-mutex
963 * Must be called with lock->wait_lock held and interrupts disabled
974 lockdep_assert_held(&lock->wait_lock); in try_to_take_rt_mutex()
978 * RT_MUTEX_HAS_WAITERS bit in @lock->owner. This forces all in try_to_take_rt_mutex()
980 * and they serialize on @lock->wait_lock. in try_to_take_rt_mutex()
985 * - There is a lock owner. The caller must fixup the in try_to_take_rt_mutex()
989 * - @task acquires the lock and there are no other in try_to_take_rt_mutex()
1028 * the lock. @task->pi_blocked_on is NULL, so it does in try_to_take_rt_mutex()
1045 * pi_lock dance.@task->pi_blocked_on is NULL in try_to_take_rt_mutex()
1054 * Clear @task->pi_blocked_on. Requires protection by in try_to_take_rt_mutex()
1055 * @task->pi_lock. Redundant operation for the @waiter == NULL in try_to_take_rt_mutex()
1059 raw_spin_lock(&task->pi_lock); in try_to_take_rt_mutex()
1060 task->pi_blocked_on = NULL; in try_to_take_rt_mutex()
1064 * waiter into @task->pi_waiters tree. in try_to_take_rt_mutex()
1068 raw_spin_unlock(&task->pi_lock); in try_to_take_rt_mutex()
1085 * This must be called with lock->wait_lock held and interrupts disabled
1098 lockdep_assert_held(&lock->wait_lock); in task_blocks_on_rt_mutex()
1105 * the other will detect the deadlock and return -EDEADLOCK, in task_blocks_on_rt_mutex()
1113 return -EDEADLK; in task_blocks_on_rt_mutex()
1115 raw_spin_lock(&task->pi_lock); in task_blocks_on_rt_mutex()
1116 waiter->task = task; in task_blocks_on_rt_mutex()
1117 waiter->lock = lock; in task_blocks_on_rt_mutex()
1125 task->pi_blocked_on = waiter; in task_blocks_on_rt_mutex()
1127 raw_spin_unlock(&task->pi_lock); in task_blocks_on_rt_mutex()
1136 raw_spin_lock(&task->pi_lock); in task_blocks_on_rt_mutex()
1138 task->pi_blocked_on = NULL; in task_blocks_on_rt_mutex()
1139 raw_spin_unlock(&task->pi_lock); in task_blocks_on_rt_mutex()
1147 raw_spin_lock(&owner->pi_lock); in task_blocks_on_rt_mutex()
1153 if (owner->pi_blocked_on) in task_blocks_on_rt_mutex()
1162 raw_spin_unlock(&owner->pi_lock); in task_blocks_on_rt_mutex()
1178 raw_spin_unlock_irq(&lock->wait_lock); in task_blocks_on_rt_mutex()
1183 raw_spin_lock_irq(&lock->wait_lock); in task_blocks_on_rt_mutex()
1190 * queue it up.
1192 * Called with lock->wait_lock held and interrupts disabled.
1199 raw_spin_lock(¤t->pi_lock); in mark_wakeup_next_waiter()
1204 * Remove it from current->pi_waiters and deboost. in mark_wakeup_next_waiter()
1207 * rt_mutex_setprio() to update p->pi_top_task before the in mark_wakeup_next_waiter()
1221 lock->owner = (void *) RT_MUTEX_HAS_WAITERS; in mark_wakeup_next_waiter()
1226 * p->pi_top_task pointer points to a blocked task). This however can in mark_wakeup_next_waiter()
1235 raw_spin_unlock(¤t->pi_lock); in mark_wakeup_next_waiter()
1252 * Slow path try-lock function:
1261 * This can be done without taking the @lock->wait_lock as in rt_mutex_slowtrylock()
1271 raw_spin_lock_irqsave(&lock->wait_lock, flags); in rt_mutex_slowtrylock()
1275 raw_spin_unlock_irqrestore(&lock->wait_lock, flags); in rt_mutex_slowtrylock()
1289 * Slow path to release a rt-mutex.
1297 raw_spin_lock_irqsave(&lock->wait_lock, flags); in rt_mutex_slowunlock()
1306 * foo->lock->owner = NULL; in rt_mutex_slowunlock()
1307 * rtmutex_lock(foo->lock); <- fast path in rt_mutex_slowunlock()
1308 * free = atomic_dec_and_test(foo->refcnt); in rt_mutex_slowunlock()
1309 * rtmutex_unlock(foo->lock); <- fast path in rt_mutex_slowunlock()
1311 * kfree(foo); in rt_mutex_slowunlock()
1312 * raw_spin_unlock(foo->lock->wait_lock); in rt_mutex_slowunlock()
1317 * lock->wait_lock. So we do the following sequence: in rt_mutex_slowunlock()
1321 * raw_spin_unlock(&lock->wait_lock); in rt_mutex_slowunlock()
1322 * if (cmpxchg(&lock->owner, owner, 0) == owner) in rt_mutex_slowunlock()
1327 * lock->owner is serialized by lock->wait_lock: in rt_mutex_slowunlock()
1329 * lock->owner = NULL; in rt_mutex_slowunlock()
1330 * raw_spin_unlock(&lock->wait_lock); in rt_mutex_slowunlock()
1333 /* Drops lock->wait_lock ! */ in rt_mutex_slowunlock()
1337 raw_spin_lock_irqsave(&lock->wait_lock, flags); in rt_mutex_slowunlock()
1344 * Queue the next waiter for wakeup once we release the wait_lock. in rt_mutex_slowunlock()
1347 raw_spin_unlock_irqrestore(&lock->wait_lock, flags); in rt_mutex_slowunlock()
1381 * - the lock owner has been scheduled out in rtmutex_spin_on_owner()
1382 * - current is not longer the top waiter in rtmutex_spin_on_owner()
1383 * - current is requested to reschedule (redundant in rtmutex_spin_on_owner()
1385 * - the VCPU on which owner runs is preempted in rtmutex_spin_on_owner()
1409 * - rtmutex, futex on all kernels
1410 * - mutex and rwsem substitutions on RT kernels
1416 * Must be called with lock->wait_lock held and interrupts disabled. It must
1426 lockdep_assert_held(&lock->wait_lock); in remove_waiter()
1428 raw_spin_lock(¤t->pi_lock); in remove_waiter()
1430 current->pi_blocked_on = NULL; in remove_waiter()
1431 raw_spin_unlock(¤t->pi_lock); in remove_waiter()
1440 raw_spin_lock(&owner->pi_lock); in remove_waiter()
1452 raw_spin_unlock(&owner->pi_lock); in remove_waiter()
1464 raw_spin_unlock_irq(&lock->wait_lock); in remove_waiter()
1469 raw_spin_lock_irq(&lock->wait_lock); in remove_waiter()
1473 * rt_mutex_slowlock_block() - Perform the wait-wake-try-to-take loop
1478 * @timeout: the pre-initialized and started timer, or NULL for none
1479 * @waiter: the pre-initialized rt_mutex_waiter
1481 * Must be called with lock->wait_lock held and interrupts disabled
1498 if (timeout && !timeout->task) { in rt_mutex_slowlock_block()
1499 ret = -ETIMEDOUT; in rt_mutex_slowlock_block()
1503 ret = -EINTR; in rt_mutex_slowlock_block()
1517 raw_spin_unlock_irq(&lock->wait_lock); in rt_mutex_slowlock_block()
1522 raw_spin_lock_irq(&lock->wait_lock); in rt_mutex_slowlock_block()
1534 * If the result is not -EDEADLOCK or the caller requested in rt_mutex_handle_deadlock()
1537 if (res != -EDEADLOCK || detect_deadlock) in rt_mutex_handle_deadlock()
1540 if (build_ww_mutex() && w->ww_ctx) in rt_mutex_handle_deadlock()
1554 * __rt_mutex_slowlock - Locking slowpath invoked with lock::wait_lock held
1571 lockdep_assert_held(&lock->wait_lock); in __rt_mutex_slowlock()
1593 if (!ww_ctx->is_wait_die) in __rt_mutex_slowlock()
1632 * rt_mutex_slowlock - Locking slowpath invoked when fast path fails
1648 * rtmutex with lock->wait_lock held. But we cannot unconditionally in rt_mutex_slowlock()
1652 raw_spin_lock_irqsave(&lock->wait_lock, flags); in rt_mutex_slowlock()
1654 raw_spin_unlock_irqrestore(&lock->wait_lock, flags); in rt_mutex_slowlock()
1675 * rtlock_slowlock_locked - Slow path lock acquisition for RT locks
1683 lockdep_assert_held(&lock->wait_lock); in rtlock_slowlock_locked()
1706 raw_spin_unlock_irq(&lock->wait_lock); in rtlock_slowlock_locked()
1711 raw_spin_lock_irq(&lock->wait_lock); in rtlock_slowlock_locked()
1732 raw_spin_lock_irqsave(&lock->wait_lock, flags); in rtlock_slowlock()
1734 raw_spin_unlock_irqrestore(&lock->wait_lock, flags); in rtlock_slowlock()