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| author | Chris Wilson <chris@chris-wilson.co.uk> | 2016-05-26 21:08:17 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-07-27 09:47:29 -0700 |
| commit | c7f47e59c31ddf80f239541ffb242d70210b36fb (patch) | |
| tree | d7f4ddbf31080b80981f330df11e398f27d10054 /kernel | |
| parent | c5f2e833575b3ad7ab59a90d66d7f1a73e7afad1 (diff) | |
| download | lwn-c7f47e59c31ddf80f239541ffb242d70210b36fb.tar.gz lwn-c7f47e59c31ddf80f239541ffb242d70210b36fb.zip | |
locking/ww_mutex: Report recursive ww_mutex locking early
commit 0422e83d84ae24b933e4b0d4c1e0f0b4ae8a0a3b upstream.
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>
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/locking/mutex.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 0551c219c40e..89350f924c85 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)) { #ifdef CONFIG_DEBUG_MUTEXES @@ -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; + } + preempt_disable(); mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); |