diff options
Diffstat (limited to 'kernel/rtmutex.c')
| -rw-r--r-- | kernel/rtmutex.c | 1138 |
1 files changed, 0 insertions, 1138 deletions
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c deleted file mode 100644 index a9604815786..00000000000 --- a/kernel/rtmutex.c +++ /dev/null @@ -1,1138 +0,0 @@ -/* - * RT-Mutexes: simple blocking mutual exclusion locks with PI support - * - * started by Ingo Molnar and Thomas Gleixner. - * - * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> - * Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> - * Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt - * Copyright (C) 2006 Esben Nielsen - * - * See Documentation/rt-mutex-design.txt for details. - */ -#include <linux/spinlock.h> -#include <linux/module.h> -#include <linux/sched.h> -#include <linux/timer.h> - -#include "rtmutex_common.h" - -/* - * lock->owner state tracking: - * - * lock->owner holds the task_struct pointer of the owner. Bit 0 and 1 - * are used to keep track of the "owner is pending" and "lock has - * waiters" state. - * - * owner bit1 bit0 - * NULL 0 0 lock is free (fast acquire possible) - * NULL 0 1 invalid state - * NULL 1 0 Transitional State* - * NULL 1 1 invalid state - * taskpointer 0 0 lock is held (fast release possible) - * taskpointer 0 1 task is pending owner - * taskpointer 1 0 lock is held and has waiters - * taskpointer 1 1 task is pending owner and lock has more waiters - * - * Pending ownership is assigned to the top (highest priority) - * waiter of the lock, when the lock is released. The thread is woken - * up and can now take the lock. Until the lock is taken (bit 0 - * cleared) a competing higher priority thread can steal the lock - * which puts the woken up thread back on the waiters list. - * - * The fast atomic compare exchange based acquire and release is only - * possible when bit 0 and 1 of lock->owner are 0. - * - * (*) There's a small time where the owner can be NULL and the - * "lock has waiters" bit is set. This can happen when grabbing the lock. - * To prevent a cmpxchg of the owner releasing the lock, we need to set this - * bit before looking at the lock, hence the reason this is a transitional - * state. - */ - -static void -rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner, - unsigned long mask) -{ - unsigned long val = (unsigned long)owner | mask; - - if (rt_mutex_has_waiters(lock)) - val |= RT_MUTEX_HAS_WAITERS; - - lock->owner = (struct task_struct *)val; -} - -static inline void clear_rt_mutex_waiters(struct rt_mutex *lock) -{ - lock->owner = (struct task_struct *) - ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS); -} - -static void fixup_rt_mutex_waiters(struct rt_mutex *lock) -{ - if (!rt_mutex_has_waiters(lock)) - clear_rt_mutex_waiters(lock); -} - -/* - * We can speed up the acquire/release, if the architecture - * supports cmpxchg and if there's no debugging state to be set up - */ -#if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES) -# define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c) -static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) -{ - unsigned long owner, *p = (unsigned long *) &lock->owner; - - do { - owner = *p; - } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner); -} -#else -# define rt_mutex_cmpxchg(l,c,n) (0) -static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) -{ - lock->owner = (struct task_struct *) - ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS); -} -#endif - -/* - * Calculate task priority from the waiter list priority - * - * Return task->normal_prio when the waiter list is empty or when - * the waiter is not allowed to do priority boosting - */ -int rt_mutex_getprio(struct task_struct *task) -{ - if (likely(!task_has_pi_waiters(task))) - return task->normal_prio; - - return min(task_top_pi_waiter(task)->pi_list_entry.prio, - task->normal_prio); -} - -/* - * Adjust the priority of a task, after its pi_waiters got modified. - * - * This can be both boosting and unboosting. task->pi_lock must be held. - */ -static void __rt_mutex_adjust_prio(struct task_struct *task) -{ - int prio = rt_mutex_getprio(task); - - if (task->prio != prio) - rt_mutex_setprio(task, prio); -} - -/* - * Adjust task priority (undo boosting). Called from the exit path of - * rt_mutex_slowunlock() and rt_mutex_slowlock(). - * - * (Note: We do this outside of the protection of lock->wait_lock to - * allow the lock to be taken while or before we readjust the priority - * of task. We do not use the spin_xx_mutex() variants here as we are - * outside of the debug path.) - */ -static void rt_mutex_adjust_prio(struct task_struct *task) -{ - unsigned long flags; - - raw_spin_lock_irqsave(&task->pi_lock, flags); - __rt_mutex_adjust_prio(task); - raw_spin_unlock_irqrestore(&task->pi_lock, flags); -} - -/* - * Max number of times we'll walk the boosting chain: - */ -int max_lock_depth = 1024; - -/* - * Adjust the priority chain. Also used for deadlock detection. - * Decreases task's usage by one - may thus free the task. - * Returns 0 or -EDEADLK. - */ -static int rt_mutex_adjust_prio_chain(struct task_struct *task, - int deadlock_detect, - struct rt_mutex *orig_lock, - struct rt_mutex_waiter *orig_waiter, - struct task_struct *top_task) -{ - struct rt_mutex *lock; - struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; - int detect_deadlock, ret = 0, depth = 0; - unsigned long flags; - - detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter, - deadlock_detect); - - /* - * The (de)boosting is a step by step approach with a lot of - * pitfalls. We want this to be preemptible and we want hold a - * maximum of two locks per step. So we have to check - * carefully whether things change under us. - */ - again: - if (++depth > max_lock_depth) { - static int prev_max; - - /* - * Print this only once. If the admin changes the limit, - * print a new message when reaching the limit again. - */ - if (prev_max != max_lock_depth) { - prev_max = max_lock_depth; - printk(KERN_WARNING "Maximum lock depth %d reached " - "task: %s (%d)\n", max_lock_depth, - top_task->comm, task_pid_nr(top_task)); - } - put_task_struct(task); - - return deadlock_detect ? -EDEADLK : 0; - } - retry: - /* - * Task can not go away as we did a get_task() before ! - */ - raw_spin_lock_irqsave(&task->pi_lock, flags); - - waiter = task->pi_blocked_on; - /* - * Check whether the end of the boosting chain has been - * reached or the state of the chain has changed while we - * dropped the locks. - */ - if (!waiter || !waiter->task) - goto out_unlock_pi; - - /* - * Check the orig_waiter state. After we dropped the locks, - * the previous owner of the lock might have released the lock - * and made us the pending owner: - */ - if (orig_waiter && !orig_waiter->task) - goto out_unlock_pi; - - /* - * Drop out, when the task has no waiters. Note, - * top_waiter can be NULL, when we are in the deboosting - * mode! - */ - if (top_waiter && (!task_has_pi_waiters(task) || - top_waiter != task_top_pi_waiter(task))) - goto out_unlock_pi; - - /* - * When deadlock detection is off then we check, if further - * priority adjustment is necessary. - */ - if (!detect_deadlock && waiter->list_entry.prio == task->prio) - goto out_unlock_pi; - - lock = waiter->lock; - if (!raw_spin_trylock(&lock->wait_lock)) { - raw_spin_unlock_irqrestore(&task->pi_lock, flags); - cpu_relax(); - goto retry; - } - - /* Deadlock detection */ - if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { - debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock); - raw_spin_unlock(&lock->wait_lock); - ret = deadlock_detect ? -EDEADLK : 0; - goto out_unlock_pi; - } - - top_waiter = rt_mutex_top_waiter(lock); - - /* Requeue the waiter */ - plist_del(&waiter->list_entry, &lock->wait_list); - waiter->list_entry.prio = task->prio; - plist_add(&waiter->list_entry, &lock->wait_list); - - /* Release the task */ - raw_spin_unlock_irqrestore(&task->pi_lock, flags); - put_task_struct(task); - - /* Grab the next task */ - task = rt_mutex_owner(lock); - get_task_struct(task); - raw_spin_lock_irqsave(&task->pi_lock, flags); - - if (waiter == rt_mutex_top_waiter(lock)) { - /* Boost the owner */ - plist_del(&top_waiter->pi_list_entry, &task->pi_waiters); - waiter->pi_list_entry.prio = waiter->list_entry.prio; - plist_add(&waiter->pi_list_entry, &task->pi_waiters); - __rt_mutex_adjust_prio(task); - - } else if (top_waiter == waiter) { - /* Deboost the owner */ - plist_del(&waiter->pi_list_entry, &task->pi_waiters); - waiter = rt_mutex_top_waiter(lock); - waiter->pi_list_entry.prio = waiter->list_entry.prio; - plist_add(&waiter->pi_list_entry, &task->pi_waiters); - __rt_mutex_adjust_prio(task); - } - - raw_spin_unlock_irqrestore(&task->pi_lock, flags); - - top_waiter = rt_mutex_top_waiter(lock); - raw_spin_unlock(&lock->wait_lock); - - if (!detect_deadlock && waiter != top_waiter) - goto out_put_task; - - goto again; - - out_unlock_pi: - raw_spin_unlock_irqrestore(&task->pi_lock, flags); - out_put_task: - put_task_struct(task); - - return ret; -} - -/* - * Optimization: check if we can steal the lock from the - * assigned pending owner [which might not have taken the - * lock yet]: - */ -static inline int try_to_steal_lock(struct rt_mutex *lock, - struct task_struct *task) -{ - struct task_struct *pendowner = rt_mutex_owner(lock); - struct rt_mutex_waiter *next; - unsigned long flags; - - if (!rt_mutex_owner_pending(lock)) - return 0; - - if (pendowner == task) - return 1; - - raw_spin_lock_irqsave(&pendowner->pi_lock, flags); - if (task->prio >= pendowner->prio) { - raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags); - return 0; - } - - /* - * Check if a waiter is enqueued on the pending owners - * pi_waiters list. Remove it and readjust pending owners - * priority. - */ - if (likely(!rt_mutex_has_waiters(lock))) { - raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags); - return 1; - } - - /* No chain handling, pending owner is not blocked on anything: */ - next = rt_mutex_top_waiter(lock); - plist_del(&next->pi_list_entry, &pendowner->pi_waiters); - __rt_mutex_adjust_prio(pendowner); - raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags); - - /* - * We are going to steal the lock and a waiter was - * enqueued on the pending owners pi_waiters queue. So - * we have to enqueue this waiter into - * task->pi_waiters list. This covers the case, - * where task is boosted because it holds another - * lock and gets unboosted because the booster is - * interrupted, so we would delay a waiter with higher - * priority as task->normal_prio. - * - * Note: in the rare case of a SCHED_OTHER task changing - * its priority and thus stealing the lock, next->task - * might be task: - */ - if (likely(next->task != task)) { - raw_spin_lock_irqsave(&task->pi_lock, flags); - plist_add(&next->pi_list_entry, &task->pi_waiters); - __rt_mutex_adjust_prio(task); - raw_spin_unlock_irqrestore(&task->pi_lock, flags); - } - return 1; -} - -/* - * Try to take an rt-mutex - * - * This fails - * - when the lock has a real owner - * - when a different pending owner exists and has higher priority than current - * - * Must be called with lock->wait_lock held. - */ -static int try_to_take_rt_mutex(struct rt_mutex *lock) -{ - /* - * We have to be careful here if the atomic speedups are - * enabled, such that, when - * - no other waiter is on the lock - * - the lock has been released since we did the cmpxchg - * the lock can be released or taken while we are doing the - * checks and marking the lock with RT_MUTEX_HAS_WAITERS. - * - * The atomic acquire/release aware variant of - * mark_rt_mutex_waiters uses a cmpxchg loop. After setting - * the WAITERS bit, the atomic release / acquire can not - * happen anymore and lock->wait_lock protects us from the - * non-atomic case. - * - * Note, that this might set lock->owner = - * RT_MUTEX_HAS_WAITERS in the case the lock is not contended - * any more. This is fixed up when we take the ownership. - * This is the transitional state explained at the top of this file. - */ - mark_rt_mutex_waiters(lock); - - if (rt_mutex_owner(lock) && !try_to_steal_lock(lock, current)) - return 0; - - /* We got the lock. */ - debug_rt_mutex_lock(lock); - - rt_mutex_set_owner(lock, current, 0); - - rt_mutex_deadlock_account_lock(lock, current); - - return 1; -} - -/* - * Task blocks on lock. - * - * Prepare waiter and propagate pi chain - * - * This must be called with lock->wait_lock held. - */ -static int task_blocks_on_rt_mutex(struct rt_mutex *lock, - struct rt_mutex_waiter *waiter, - struct task_struct *task, - int detect_deadlock) -{ - struct task_struct *owner = rt_mutex_owner(lock); - struct rt_mutex_waiter *top_waiter = waiter; - unsigned long flags; - int chain_walk = 0, res; - - raw_spin_lock_irqsave(&task->pi_lock, flags); - __rt_mutex_adjust_prio(task); - waiter->task = task; - waiter->lock = lock; - plist_node_init(&waiter->list_entry, task->prio); - plist_node_init(&waiter->pi_list_entry, task->prio); - - /* Get the top priority waiter on the lock */ - if (rt_mutex_has_waiters(lock)) - top_waiter = rt_mutex_top_waiter(lock); - plist_add(&waiter->list_entry, &lock->wait_list); - - task->pi_blocked_on = waiter; - - raw_spin_unlock_irqrestore(&task->pi_lock, flags); - - if (waiter == rt_mutex_top_waiter(lock)) { - raw_spin_lock_irqsave(&owner->pi_lock, flags); - plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters); - plist_add(&waiter->pi_list_entry, &owner->pi_waiters); - - __rt_mutex_adjust_prio(owner); - if (owner->pi_blocked_on) - chain_walk = 1; - raw_spin_unlock_irqrestore(&owner->pi_lock, flags); - } - else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) - chain_walk = 1; - - if (!chain_walk) - return 0; - - /* - * The owner can't disappear while holding a lock, - * so the owner struct is protected by wait_lock. - * Gets dropped in rt_mutex_adjust_prio_chain()! - */ - get_task_struct(owner); - - raw_spin_unlock(&lock->wait_lock); - - res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter, - task); - - raw_spin_lock(&lock->wait_lock); - - return res; -} - -/* - * Wake up the next waiter on the lock. - * - * Remove the top waiter from the current tasks waiter list and from - * the lock waiter list. Set it as pending owner. Then wake it up. - * - * Called with lock->wait_lock held. - */ -static void wakeup_next_waiter(struct rt_mutex *lock) -{ - struct rt_mutex_waiter *waiter; - struct task_struct *pendowner; - unsigned long flags; - - raw_spin_lock_irqsave(¤t->pi_lock, flags); - - waiter = rt_mutex_top_waiter(lock); - plist_del(&waiter->list_entry, &lock->wait_list); - - /* - * Remove it from current->pi_waiters. We do not adjust a - * possible priority boost right now. We execute wakeup in the - * boosted mode and go back to normal after releasing - * lock->wait_lock. - */ - plist_del(&waiter->pi_list_entry, ¤t->pi_waiters); - pendowner = waiter->task; - waiter->task = NULL; - - rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING); - - raw_spin_unlock_irqrestore(¤t->pi_lock, flags); - - /* - * Clear the pi_blocked_on variable and enqueue a possible - * waiter into the pi_waiters list of the pending owner. This - * prevents that in case the pending owner gets unboosted a - * waiter with higher priority than pending-owner->normal_prio - * is blocked on the unboosted (pending) owner. - */ - raw_spin_lock_irqsave(&pendowner->pi_lock, flags); - - WARN_ON(!pendowner->pi_blocked_on); - WARN_ON(pendowner->pi_blocked_on != waiter); - WARN_ON(pendowner->pi_blocked_on->lock != lock); - - pendowner->pi_blocked_on = NULL; - - if (rt_mutex_has_waiters(lock)) { - struct rt_mutex_waiter *next; - - next = rt_mutex_top_waiter(lock); - plist_add(&next->pi_list_entry, &pendowner->pi_waiters); - } - raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags); - - wake_up_process(pendowner); -} - -/* - * Remove a waiter from a lock - * - * Must be called with lock->wait_lock held - */ -static void remove_waiter(struct rt_mutex *lock, - struct rt_mutex_waiter *waiter) -{ - int first = (waiter == rt_mutex_top_waiter(lock)); - struct task_struct *owner = rt_mutex_owner(lock); - unsigned long flags; - int chain_walk = 0; - - raw_spin_lock_irqsave(¤t->pi_lock, flags); - plist_del(&waiter->list_entry, &lock->wait_list); - waiter->task = NULL; - current->pi_blocked_on = NULL; - raw_spin_unlock_irqrestore(¤t->pi_lock, flags); - - if (first && owner != current) { - - raw_spin_lock_irqsave(&owner->pi_lock, flags); - - plist_del(&waiter->pi_list_entry, &owner->pi_waiters); - - if (rt_mutex_has_waiters(lock)) { - struct rt_mutex_waiter *next; - - next = rt_mutex_top_waiter(lock); - plist_add(&next->pi_list_entry, &owner->pi_waiters); - } - __rt_mutex_adjust_prio(owner); - - if (owner->pi_blocked_on) - chain_walk = 1; - - raw_spin_unlock_irqrestore(&owner->pi_lock, flags); - } - - WARN_ON(!plist_node_empty(&waiter->pi_list_entry)); - - if (!chain_walk) - return; - - /* gets dropped in rt_mutex_adjust_prio_chain()! */ - get_task_struct(owner); - - raw_spin_unlock(&lock->wait_lock); - - rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current); - - raw_spin_lock(&lock->wait_lock); -} - -/* - * Recheck the pi chain, in case we got a priority setting - * - * Called from sched_setscheduler - */ -void rt_mutex_adjust_pi(struct task_struct *task) -{ - struct rt_mutex_waiter *waiter; - unsigned long flags; - - raw_spin_lock_irqsave(&task->pi_lock, flags); - - waiter = task->pi_blocked_on; - if (!waiter || waiter->list_entry.prio == task->prio) { - raw_spin_unlock_irqrestore(&task->pi_lock, flags); - return; - } - - raw_spin_unlock_irqrestore(&task->pi_lock, flags); - - /* gets dropped in rt_mutex_adjust_prio_chain()! */ - get_task_struct(task); - rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task); -} - -/** - * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop - * @lock: the rt_mutex to take - * @state: the state the task should block in (TASK_INTERRUPTIBLE - * or TASK_UNINTERRUPTIBLE) - * @timeout: the pre-initialized and started timer, or NULL for none - * @waiter: the pre-initialized rt_mutex_waiter - * @detect_deadlock: passed to task_blocks_on_rt_mutex - * - * lock->wait_lock must be held by the caller. - */ -static int __sched -__rt_mutex_slowlock(struct rt_mutex *lock, int state, - struct hrtimer_sleeper *timeout, - struct rt_mutex_waiter *waiter, - int detect_deadlock) -{ - int ret = 0; - - for (;;) { - /* Try to acquire the lock: */ - if (try_to_take_rt_mutex(lock)) - break; - - /* - * TASK_INTERRUPTIBLE checks for signals and - * timeout. Ignored otherwise. - */ - if (unlikely(state == TASK_INTERRUPTIBLE)) { - /* Signal pending? */ - if (signal_pending(current)) - ret = -EINTR; - if (timeout && !timeout->task) - ret = -ETIMEDOUT; - if (ret) - break; - } - - /* - * waiter->task is NULL the first time we come here and - * when we have been woken up by the previous owner - * but the lock got stolen by a higher prio task. - */ - if (!waiter->task) { - ret = task_blocks_on_rt_mutex(lock, waiter, current, - detect_deadlock); - /* - * If we got woken up by the owner then start loop - * all over without going into schedule to try - * to get the lock now: - */ - if (unlikely(!waiter->task)) { - /* - * Reset the return value. We might - * have returned with -EDEADLK and the - * owner released the lock while we - * were walking the pi chain. - */ - ret = 0; - continue; - } - if (unlikely(ret)) - break; - } - - raw_spin_unlock(&lock->wait_lock); - - debug_rt_mutex_print_deadlock(waiter); - - if (waiter->task) - schedule_rt_mutex(lock); - - raw_spin_lock(&lock->wait_lock); - set_current_state(state); - } - - return ret; -} - -/* - * Slow path lock function: - */ -static int __sched -rt_mutex_slowlock(struct rt_mutex *lock, int state, - struct hrtimer_sleeper *timeout, - int detect_deadlock) -{ - struct rt_mutex_waiter waiter; - int ret = 0; - - debug_rt_mutex_init_waiter(&waiter); - waiter.task = NULL; - - raw_spin_lock(&lock->wait_lock); - - /* Try to acquire the lock again: */ - if (try_to_take_rt_mutex(lock)) { - raw_spin_unlock(&lock->wait_lock); - return 0; - } - - set_current_state(state); - - /* Setup the timer, when timeout != NULL */ - if (unlikely(timeout)) { - hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); - if (!hrtimer_active(&timeout->timer)) - timeout->task = NULL; - } - - ret = __rt_mutex_slowlock(lock, state, timeout, &waiter, - detect_deadlock); - - set_current_state(TASK_RUNNING); - - if (unlikely(waiter.task)) - remove_waiter(lock, &waiter); - - /* - * try_to_take_rt_mutex() sets the waiter bit - * unconditionally. We might have to fix that up. - */ - fixup_rt_mutex_waiters(lock); - - raw_spin_unlock(&lock->wait_lock); - - /* Remove pending timer: */ - if (unlikely(timeout)) - hrtimer_cancel(&timeout->timer); - - /* - * Readjust priority, when we did not get the lock. We might - * have been the pending owner and boosted. Since we did not - * take the lock, the PI boost has to go. - */ - if (unlikely(ret)) - rt_mutex_adjust_prio(current); - - debug_rt_mutex_free_waiter(&waiter); - - return ret; -} - -/* - * Slow path try-lock function: - */ -static inline int -rt_mutex_slowtrylock(struct rt_mutex *lock) -{ - int ret = 0; - - raw_spin_lock(&lock->wait_lock); - - if (likely(rt_mutex_owner(lock) != current)) { - - ret = try_to_take_rt_mutex(lock); - /* - * try_to_take_rt_mutex() sets the lock waiters - * bit unconditionally. Clean this up. - */ - fixup_rt_mutex_waiters(lock); - } - - raw_spin_unlock(&lock->wait_lock); - - return ret; -} - -/* - * Slow path to release a rt-mutex: - */ -static void __sched -rt_mutex_slowunlock(struct rt_mutex *lock) -{ - raw_spin_lock(&lock->wait_lock); - - debug_rt_mutex_unlock(lock); - - rt_mutex_deadlock_account_unlock(current); - - if (!rt_mutex_has_waiters(lock)) { - lock->owner = NULL; - raw_spin_unlock(&lock->wait_lock); - return; - } - - wakeup_next_waiter(lock); - - raw_spin_unlock(&lock->wait_lock); - - /* Undo pi boosting if necessary: */ - rt_mutex_adjust_prio(current); -} - -/* - * debug aware fast / slowpath lock,trylock,unlock - * - * The atomic acquire/release ops are compiled away, when either the - * architecture does not support cmpxchg or when debugging is enabled. - */ -static inline int -rt_mutex_fastlock(struct rt_mutex *lock, int state, - int detect_deadlock, - int (*slowfn)(struct rt_mutex *lock, int state, - struct hrtimer_sleeper *timeout, - int detect_deadlock)) -{ - if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { - rt_mutex_deadlock_account_lock(lock, current); - return 0; - } else - return slowfn(lock, state, NULL, detect_deadlock); -} - -static inline int -rt_mutex_timed_fastlock(struct rt_mutex *lock, int state, - struct hrtimer_sleeper *timeout, int detect_deadlock, - int (*slowfn)(struct rt_mutex *lock, int state, - struct hrtimer_sleeper *timeout, - int detect_deadlock)) -{ - if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { - rt_mutex_deadlock_account_lock(lock, current); - return 0; - } else - return slowfn(lock, state, timeout, detect_deadlock); -} - -static inline int -rt_mutex_fasttrylock(struct rt_mutex *lock, - int (*slowfn)(struct rt_mutex *lock)) -{ - if (likely(rt_mutex_cmpxchg(lock, NULL, current))) { - rt_mutex_deadlock_account_lock(lock, current); - return 1; - } - return slowfn(lock); -} - -static inline void -rt_mutex_fastunlock(struct rt_mutex *lock, - void (*slowfn)(struct rt_mutex *lock)) -{ - if (likely(rt_mutex_cmpxchg(lock, current, NULL))) - rt_mutex_deadlock_account_unlock(current); - else - slowfn(lock); -} - -/** - * rt_mutex_lock - lock a rt_mutex - * - * @lock: the rt_mutex to be locked - */ -void __sched rt_mutex_lock(struct rt_mutex *lock) -{ - might_sleep(); - - rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock); -} -EXPORT_SYMBOL_GPL(rt_mutex_lock); - -/** - * rt_mutex_lock_interruptible - lock a rt_mutex interruptible - * - * @lock: the rt_mutex to be locked - * @detect_deadlock: deadlock detection on/off - * - * Returns: - * 0 on success - * -EINTR when interrupted by a signal - * -EDEADLK when the lock would deadlock (when deadlock detection is on) - */ -int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock, - int detect_deadlock) -{ - might_sleep(); - - return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, - detect_deadlock, rt_mutex_slowlock); -} -EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible); - -/** - * rt_mutex_timed_lock - lock a rt_mutex interruptible - * the timeout structure is provided - * by the caller - * - * @lock: the rt_mutex to be locked - * @timeout: timeout structure or NULL (no timeout) - * @detect_deadlock: deadlock detection on/off - * - * Returns: - * 0 on success - * -EINTR when interrupted by a signal - * -ETIMEDOUT when the timeout expired - * -EDEADLK when the lock would deadlock (when deadlock detection is on) - */ -int -rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout, - int detect_deadlock) -{ - might_sleep(); - - return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, - detect_deadlock, rt_mutex_slowlock); -} -EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); - -/** - * rt_mutex_trylock - try to lock a rt_mutex - * - * @lock: the rt_mutex to be locked - * - * Returns 1 on success and 0 on contention - */ -int __sched rt_mutex_trylock(struct rt_mutex *lock) -{ - return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock); -} -EXPORT_SYMBOL_GPL(rt_mutex_trylock); - -/** - * rt_mutex_unlock - unlock a rt_mutex - * - * @lock: the rt_mutex to be unlocked - */ -void __sched rt_mutex_unlock(struct rt_mutex *lock) -{ - rt_mutex_fastunlock(lock, rt_mutex_slowunlock); -} -EXPORT_SYMBOL_GPL(rt_mutex_unlock); - -/** - * rt_mutex_destroy - mark a mutex unusable - * @lock: the mutex to be destroyed - * - * This function marks the mutex uninitialized, and any subsequent - * use of the mutex is forbidden. The mutex must not be locked when - * this function is called. - */ -void rt_mutex_destroy(struct rt_mutex *lock) -{ - WARN_ON(rt_mutex_is_locked(lock)); -#ifdef CONFIG_DEBUG_RT_MUTEXES - lock->magic = NULL; -#endif -} - -EXPORT_SYMBOL_GPL(rt_mutex_destroy); - -/** - * __rt_mutex_init - initialize the rt lock - * - * @lock: the rt lock to be initialized - * - * Initialize the rt lock to unlocked state. - * - * Initializing of a locked rt lock is not allowed - */ -void __rt_mutex_init(struct rt_mutex *lock, const char *name) -{ - lock->owner = NULL; - raw_spin_lock_init(&lock->wait_lock); - plist_head_init_raw(&lock->wait_list, &lock->wait_lock); - - debug_rt_mutex_init(lock, name); -} -EXPORT_SYMBOL_GPL(__rt_mutex_init); - -/** - * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a - * proxy owner - * - * @lock: the rt_mutex to be locked - * @proxy_owner:the task to set as owner - * - * No locking. Caller has to do serializing itself - * Special API call for PI-futex support - */ -void rt_mutex_init_proxy_locked(struct rt_mutex *lock, - struct task_struct *proxy_owner) -{ - __rt_mutex_init(lock, NULL); - debug_rt_mutex_proxy_lock(lock, proxy_owner); - rt_mutex_set_owner(lock, proxy_owner, 0); - rt_mutex_deadlock_account_lock(lock, proxy_owner); -} - -/** - * rt_mutex_proxy_unlock - release a lock on behalf of owner - * - * @lock: the rt_mutex to be locked - * - * No locking. Caller has to do serializing itself - * Special API call for PI-futex support - */ -void rt_mutex_proxy_unlock(struct rt_mutex *lock, - struct task_struct *proxy_owner) -{ - debug_rt_mutex_proxy_unlock(lock); - rt_mutex_set_owner(lock, NULL, 0); - rt_mutex_deadlock_account_unlock(proxy_owner); -} - -/** - * rt_mutex_start_proxy_lock() - Start lock acquisition for another task - * @lock: the rt_mutex to take - * @waiter: the pre-initialized rt_mutex_waiter - * @task: the task to prepare - * @detect_deadlock: perform deadlock detection (1) or not (0) - * - * Returns: - * 0 - task blocked on lock - * 1 - acquired the lock for task, caller should wake it up - * <0 - error - * - * Special API call for FUTEX_REQUEUE_PI support. - */ -int rt_mutex_start_proxy_lock(struct rt_mutex *lock, - struct rt_mutex_waiter *waiter, - struct task_struct *task, int detect_deadlock) -{ - int ret; - - raw_spin_lock(&lock->wait_lock); - - mark_rt_mutex_waiters(lock); - - if (!rt_mutex_owner(lock) || try_to_steal_lock(lock, task)) { - /* We got the lock for task. */ - debug_rt_mutex_lock(lock); - rt_mutex_set_owner(lock, task, 0); - raw_spin_unlock(&lock->wait_lock); - rt_mutex_deadlock_account_lock(lock, task); - return 1; - } - - ret = task_blocks_on_rt_mutex(lock, waiter, task, detect_deadlock); - - if (ret && !waiter->task) { - /* - * Reset the return value. We might have - * returned with -EDEADLK and the owner - * released the lock while we were walking the - * pi chain. Let the waiter sort it out. - */ - ret = 0; - } - raw_spin_unlock(&lock->wait_lock); - - debug_rt_mutex_print_deadlock(waiter); - - return ret; -} - -/** - * rt_mutex_next_owner - return the next owner of the lock - * - * @lock: the rt lock query - * - * Returns the next owner of the lock or NULL - * - * Caller has to serialize against other accessors to the lock - * itself. - * - * Special API call for PI-futex support - */ -struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock) -{ - if (!rt_mutex_has_waiters(lock)) - return NULL; - - return rt_mutex_top_waiter(lock)->task; -} - -/** - * rt_mutex_finish_proxy_lock() - Complete lock acquisition - * @lock: the rt_mutex we were woken on - * @to: the timeout, null if none. hrtimer should already have - * been started. - * @waiter: the pre-initialized rt_mutex_waiter - * @detect_deadlock: perform deadlock detection (1) or not (0) - * - * Complete the lock acquisition started our behalf by another thread. - * - * Returns: - * 0 - success - * <0 - error, one of -EINTR, -ETIMEDOUT, or -EDEADLK - * - * Special API call for PI-futex requeue support - */ -int rt_mutex_finish_proxy_lock(struct rt_mutex *lock, - struct hrtimer_sleeper *to, - struct rt_mutex_waiter *waiter, - int detect_deadlock) -{ - int ret; - - raw_spin_lock(&lock->wait_lock); - - set_current_state(TASK_INTERRUPTIBLE); - - ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter, - detect_deadlock); - - set_current_state(TASK_RUNNING); - - if (unlikely(waiter->task)) - remove_waiter(lock, waiter); - - /* - * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might - * have to fix that up. - */ - fixup_rt_mutex_waiters(lock); - - raw_spin_unlock(&lock->wait_lock); - - /* - * Readjust priority, when we did not get the lock. We might have been - * the pending owner and boosted. Since we did not take the lock, the - * PI boost has to go. - */ - if (unlikely(ret)) - rt_mutex_adjust_prio(current); - - return ret; -} |