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authorChris Wilson <chris@chris-wilson.co.uk>2016-05-26 21:08:17 +0100
committerSasha Levin <sasha.levin@oracle.com>2016-06-19 23:47:43 -0400
commit33fae4cc30d0451479f620af8846c5d717f08b7b (patch)
tree3a938c7455f6a49330380f69124bae1b210de3ba
parentd822ea89aa219e61c91afbe4136e42502d08f85b (diff)
downloadlinux-linaro-stable-33fae4cc30d0451479f620af8846c5d717f08b7b.tar.gz
locking/ww_mutex: Report recursive ww_mutex locking early
[ Upstream commit 0422e83d84ae24b933e4b0d4c1e0f0b4ae8a0a3b ] Recursive locking for ww_mutexes was originally conceived as an exception. However, it is heavily used by the DRM atomic modesetting code. Currently, the recursive deadlock is checked after we have queued up for a busy-spin and as we never release the lock, we spin until kicked, whereupon the deadlock is discovered and reported. A simple solution for the now common problem is to move the recursive deadlock discovery to the first action when taking the ww_mutex. Suggested-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1464293297-19777-1-git-send-email-chris@chris-wilson.co.uk Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
-rw-r--r--kernel/locking/mutex.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index dadbf88c22c4..e3fe1dda72ca 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -471,9 +471,6 @@ __mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
if (!hold_ctx)
return 0;
- if (unlikely(ctx == hold_ctx))
- return -EALREADY;
-
if (ctx->stamp - hold_ctx->stamp <= LONG_MAX &&
(ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) {
#ifdef CONFIG_DEBUG_MUTEXES
@@ -499,6 +496,12 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
unsigned long flags;
int ret;
+ if (use_ww_ctx) {
+ struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
+ if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
+ return -EALREADY;
+ }
+
preempt_disable();
mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);