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locking: ww_mutex: fix ww_mutex vs self-deadlock 

If the caller already holds the mutex, task_blocks_on_rt_mutex()
returns -EDEADLK, we proceed directly to rt_mutex_handle_deadlock()
where it's instant game over.

Let ww_mutexes return EDEADLK/EALREADY as they want to instead.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Mike Galbraith 2015-02-26 09:02:05 +01:00 committed by Alibek Omarov
parent d12e92f871
commit faa7968040
1 changed files with 14 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
kernel/locking/rtmutex.c
View File

@ -1694,13 +1694,20 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
if (likely(!ret))
ret = __rt_mutex_slowlock(lock, state, timeout, &waiter, ww_ctx);
else if (ww_ctx) {
/* ww_mutex received EDEADLK, let it become EALREADY */
ret = __mutex_lock_check_stamp(lock, ww_ctx);
BUG_ON(!ret);
}
set_current_state(TASK_RUNNING);
if (unlikely(ret)) {
if (rt_mutex_has_waiters(lock))
remove_waiter(lock, &waiter);
rt_mutex_handle_deadlock(ret, chwalk, &waiter);
/* ww_mutex want to report EDEADLK/EALREADY, let them */
if (!ww_ctx)
rt_mutex_handle_deadlock(ret, chwalk, &waiter);
} else if (ww_ctx) {
ww_mutex_account_lock(lock, ww_ctx);
}
@ -2239,8 +2246,7 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ww_c
might_sleep();
mutex_acquire_nest(&lock->base.dep_map, 0, 0, &ww_ctx->dep_map, _RET_IP_);
ret = rt_mutex_slowlock(&lock->base.lock, TASK_INTERRUPTIBLE, NULL,
RT_MUTEX_FULL_CHAINWALK, ww_ctx);
ret = rt_mutex_slowlock(&lock->base.lock, TASK_INTERRUPTIBLE, NULL, 0, ww_ctx);
if (ret)
mutex_release(&lock->base.dep_map, 1, _RET_IP_);
else if (!ret && ww_ctx->acquired > 1)
@ -2258,8 +2264,7 @@ __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ww_ctx)
might_sleep();
mutex_acquire_nest(&lock->base.dep_map, 0, 0, &ww_ctx->dep_map, _RET_IP_);
ret = rt_mutex_slowlock(&lock->base.lock, TASK_UNINTERRUPTIBLE, NULL,
RT_MUTEX_FULL_CHAINWALK, ww_ctx);
ret = rt_mutex_slowlock(&lock->base.lock, TASK_UNINTERRUPTIBLE, NULL, 0, ww_ctx);
if (ret)
mutex_release(&lock->base.dep_map, 1, _RET_IP_);
else if (!ret && ww_ctx->acquired > 1)
@ -2271,11 +2276,13 @@ EXPORT_SYMBOL_GPL(__ww_mutex_lock);
void __sched ww_mutex_unlock(struct ww_mutex *lock)
{
int nest = !!lock->ctx;
/*
* The unlocking fastpath is the 0->1 transition from 'locked'
* into 'unlocked' state:
*/
if (lock->ctx) {
if (nest) {
#ifdef CONFIG_DEBUG_MUTEXES
DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired);
#endif
@ -2284,7 +2291,7 @@ void __sched ww_mutex_unlock(struct ww_mutex *lock)
lock->ctx = NULL;
}
mutex_release(&lock->base.dep_map, 1, _RET_IP_);
mutex_release(&lock->base.dep_map, nest, _RET_IP_);
rt_mutex_unlock(&lock->base.lock);
}
EXPORT_SYMBOL(ww_mutex_unlock);