Commit 85f48961 authored Jul 30, 2013 by Maarten Lankhorst Committed by Ingo Molnar Jul 30, 2013

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>

parent 36f571e9

kernel/mutex.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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;