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Date: Mon, 09 Mar 2015 13:14:54 -0700 From: Jason Low <jason.low2@...com> To: Peter Zijlstra <peterz@...radead.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Ingo Molnar <mingo@...nel.org>, Davidlohr Bueso <dave@...olabs.net> Cc: LKML <linux-kernel@...r.kernel.org>, Jason Low <jason.low2@...com> Subject: [PATCH] locking/mutex: Refactor mutex_spin_on_owner() This patch applies on top of tip. ------------------------------------------------------------------- Similar to what Linus suggested for rwsem_spin_on_owner(), in mutex_spin_on_owner(), instead of having while (true) and breaking out of the spin loop on lock->owner != owner, we can have the loop directly check for while (lock->owner == owner). This improves the readability of the code. Signed-off-by: Jason Low <jason.low2@...com> --- kernel/locking/mutex.c | 17 +++++------------ 1 files changed, 5 insertions(+), 12 deletions(-) diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 16b2d3c..1c3b7c5 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -224,16 +224,8 @@ ww_mutex_set_context_slowpath(struct ww_mutex *lock, static noinline bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) { - bool ret; - rcu_read_lock(); - while (true) { - /* Return success when the lock owner changed */ - if (lock->owner != owner) { - ret = true; - break; - } - + while (lock->owner == owner) { /* * Ensure we emit the owner->on_cpu, dereference _after_ * checking lock->owner still matches owner, if that fails, @@ -242,16 +234,17 @@ bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) */ barrier(); + /* Stop spinning when need_resched or owner is not running. */ if (!owner->on_cpu || need_resched()) { - ret = false; - break; + rcu_read_unlock(); + return false; } cpu_relax_lowlatency(); } rcu_read_unlock(); - return ret; + return true; } /* -- 1.7.2.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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