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authorChris Wilson <chris@chris-wilson.co.uk>2016-05-26 21:08:17 +0100
committerIngo Molnar <mingo@kernel.org>2016-06-03 08:37:26 +0200
commit0422e83d84ae24b933e4b0d4c1e0f0b4ae8a0a3b (patch)
parent55eed755c6e30a89be3a791a6b0ad208aadd9bdc (diff)
locking/ww_mutex: Report recursive ww_mutex locking early
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>
1 files changed, 6 insertions, 3 deletions
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index e364b424b019..79d2d765a75f 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -486,9 +486,6 @@ __ww_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)) {
@@ -514,6 +511,12 @@ __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;
+ }
mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);