From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maarten Lankhorst Subject: [PATCH] mutex: fix deadlock injection Date: Tue, 30 Jul 2013 10:13:41 +0200 Message-ID: <51F775B5.201@canonical.com> References: <20130701082221.GA14112@gmail.com> <51D3C4C8.8060701@canonical.com> <20130705062345.GA29487@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130705062345.GA29487@gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: Ingo Molnar Cc: Linus Torvalds , Linux Kernel Mailing List , Peter Zijlstra , Thomas Gleixner , Andrew Morton , Dave Airlie , "dri-devel@lists.freedesktop.org" , Alex Deucher List-Id: dri-devel@lists.freedesktop.org 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. Cc: Alex Deucher Signed-off-by: Maarten Lankhorst --- diff --git a/kernel/mutex.c b/kernel/mutex.c index ff05f4b..a52ee7bb 100644 --- a/kernel/mutex.c +++ b/kernel/mutex.c @@ -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;