On Wed, 07 Jan 2015, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > On Wed, Jan 07, 2015 at 02:12:14PM +0200, Jani Nikula wrote: >> On Mon, 05 Jan 2015, Daniel Vetter <daniel@xxxxxxxx> wrote: >> > On Fri, Jan 02, 2015 at 09:47:10AM +0000, Chris Wilson wrote: >> >> If CONFIG_DEBUG_MUTEXES is set, the mutex->owner field is only cleared >> >> if the mutex debugging is enabled which introduces a race in our >> >> mutex_is_locked_by() - i.e. we may inspect the old owner value before it >> >> is acquired by the new task. >> >> >> >> This is the root cause of this error: >> >> >> >> diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c >> >> index 5cf6731..3ef3736 100644 >> >> --- a/kernel/locking/mutex-debug.c >> >> +++ b/kernel/locking/mutex-debug.c >> >> @@ -80,13 +80,13 @@ void debug_mutex_unlock(struct mutex *lock) >> >> DEBUG_LOCKS_WARN_ON(lock->owner != current); >> >> >> >> DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next); >> >> - mutex_clear_owner(lock); >> >> } >> >> >> >> /* >> >> * __mutex_slowpath_needs_to_unlock() is explicitly 0 for debug >> >> * mutexes so that we can do it here after we've verified state. >> >> */ >> >> + mutex_clear_owner(lock); >> >> atomic_set(&lock->count, 1); >> >> } >> >> >> >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=87955 >> >> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> >> >> Cc: stable@xxxxxxxxxxxxxxx >> > >> > Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> >> >> Pushed to drm-intel-fixes, thanks for the patch and review. > > For the record, I plan to post a revert of this to -next if the core fix > lands upstream (looks good so far). Does it look like that could be cc:stable? BR, Jani. > -Chris > > -- > Chris Wilson, Intel Open Source Technology Centre -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
