From: Davidlohr Bueso Date: Tue, 6 Jan 2015 19:45:05 +0000 (-0800) Subject: locking/mutex: Move MCS related comments to proper location X-Git-Tag: v4.0-rc1~164^2~13 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=e42f678a0237f84f0004fbaf0fad0b844751eadd;p=linux.git locking/mutex: Move MCS related comments to proper location It serves much better if the comments are right before the osq_lock() call. Also delete a useless comment. Signed-off-by: Davidlohr Bueso Signed-off-by: Peter Zijlstra (Intel) Cc: "Paul E. McKenney" Cc: Thomas Gleixner Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1420573509-24774-3-git-send-email-dave@stgolabs.net Signed-off-by: Ingo Molnar --- diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index b042ea57bbea..6db3d0dea6da 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -193,17 +193,6 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock, #ifdef CONFIG_MUTEX_SPIN_ON_OWNER -/* - * In order to avoid a stampede of mutex spinners from acquiring the mutex - * more or less simultaneously, the spinners need to acquire a MCS lock - * first before spinning on the owner field. - * - */ - -/* - * Mutex spinning code migrated from kernel/sched/core.c - */ - static inline bool owner_running(struct mutex *lock, struct task_struct *owner) { if (lock->owner != owner) @@ -307,6 +296,11 @@ static bool mutex_optimistic_spin(struct mutex *lock, if (!mutex_can_spin_on_owner(lock)) goto done; + /* + * In order to avoid a stampede of mutex spinners trying to + * acquire the mutex all at once, the spinners need to take a + * MCS (queued) lock first before spinning on the owner field. + */ if (!osq_lock(&lock->osq)) goto done;