linux-2.6.33/__mutex_lock_common() の履歴(No.1)

• 履歴一覧
• 差分 を表示
• 現在との差分 を表示
• ソース を表示
• linux-2.6.33/__mutex_lock_common() へ行く。
  • 1 (2010-11-12 (金) 12:10:59)
  • 2 (2010-11-12 (金) 12:18:06)

参照元†

• linux-2.6.33/__mutex_lock_slowpath()

説明†

• パス: linux-2.6.33/kernel/mutex.c

• FIXME: これは何？
  • 説明

引数†

• struct mutex *lock
  • linux-2.6.33/mutex
• long state
• unsigned int subclass
• unsigned long ip

返り値†

• int

参考†

実装†

/*
 * Lock a mutex (possibly interruptible), slowpath:
 */
static inline int __sched
__mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
	       	unsigned long ip)
{
	struct task_struct *task = current;
	struct mutex_waiter waiter;
	unsigned long flags;

• • linux-2.6.33/current(global)

• linux-2.6.33/task_struct

• • linux-2.6.33/mutex_waiter

	preempt_disable();
	mutex_acquire(&lock->dep_map, subclass, 0, ip);

• • linux-2.6.33/preempt_disable()

• linux-2.6.33/mutex_acquire()

#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.
	 */

	for (;;) {
		struct thread_info *owner;

		/*
		 * If there's an owner, wait for it to either
		 * release the lock or go to sleep.
		 */
		owner = ACCESS_ONCE(lock->owner);
		if (owner && !mutex_spin_on_owner(lock, owner))
			break;

		if (atomic_cmpxchg(&lock->count, 1, 0) == 1) {
			lock_acquired(&lock->dep_map, ip);
			mutex_set_owner(lock);
			preempt_enable();
			return 0;
		}

		/*
		 * 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.
		 */
		cpu_relax();
	}
#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 (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 (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))) {
			mutex_remove_waiter(lock, &waiter,
					    task_thread_info(task));
			mutex_release(&lock->dep_map, 1, ip);
			spin_unlock_mutex(&lock->wait_lock, flags);

			debug_mutex_free_waiter(&waiter);
			preempt_enable();
			return -EINTR;
		}
		__set_task_state(task, state);

		/* didnt get the lock, go to sleep: */
		spin_unlock_mutex(&lock->wait_lock, flags);
		preempt_enable_no_resched();
		schedule();
		preempt_disable();
		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);

	/* 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;
}

コメント†