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authorMike Galbraith <umgwanakikbuti@gmail.com>2015-02-26 09:02:05 +0100
committerAnders Roxell <anders.roxell@linaro.org>2015-06-01 12:03:37 +0200
commit2a48b7a55e80abcb26a7e0f37437199fa7733186 (patch)
tree414fc5f471f3db76fb0a25e842860c7c3a0fc701
parent8281e990b1360c55798223cc914ad12d5142a82a (diff)
downloadlinux-linaro-stable-2a48b7a55e80abcb26a7e0f37437199fa7733186.tar.gz
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>
-rw-r--r--kernel/locking/rtmutex.c21
1 files changed, 14 insertions, 7 deletions
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 27a1993111f9..ee4e7e747e06 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -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);