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mutex: Fix w/w mutex deadlock injection 

The check needs to be for > 1, because ctx->acquired is already incremented.
This will prevent ww_mutex_lock_slow from returning -EDEADLK and not locking
the mutex. It caused a lot of false gpu lockups on radeon with
CONFIG_DEBUG_WW_MUTEX_SLOWPATH=y because a function that shouldn't be able
to return -EDEADLK did.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/51F775B5.201@canonical.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Maarten Lankhorst 2013-07-30 10:13:41 +02:00 committed by Ingo Molnar
parent 36f571e9ed
commit 85f4896123
1 changed files with 2 additions and 2 deletions
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4
kernel/mutex.c
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@ -686,7 +686,7 @@ __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
might_sleep();
ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
0, &ctx->dep_map, _RET_IP_, ctx);
if (!ret && ctx->acquired > 0)
if (!ret && ctx->acquired > 1)
return ww_mutex_deadlock_injection(lock, ctx);
return ret;
@ -702,7 +702,7 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
0, &ctx->dep_map, _RET_IP_, ctx);
if (!ret && ctx->acquired > 0)
if (!ret && ctx->acquired > 1)
return ww_mutex_deadlock_injection(lock, ctx);
return ret;