Re: [PATCH -v4 8/8] locking/mutex: Enable optimistic spinning of woken waiter

[Waiman Long]

On 10/07/2016 10:52 AM, Peter Zijlstra wrote:
@@ -600,7 +630,7 @@ __mutex_lock_common(struct mutex *lock,
        mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
        if (__mutex_trylock(lock, false) ||
-           mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx)) {
+           mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, false)) {
                /* got the lock, yay! */
                lock_acquired(&lock->dep_map, ip);
                if (use_ww_ctx)
@@ -669,7 +699,8 @@ __mutex_lock_common(struct mutex *lock,
                 * state back to RUNNING and fall through the next schedule(),
                 * or we must see its unlock and acquire.
                 */
-               if (__mutex_trylock(lock, first))
+               if ((first&&  mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, 
true)) ||
+                    __mutex_trylock(lock, first))

Do we need a __mutex_trylock() here? mutex_optimistic_spin() will do the 
trylock and we have one at the top of the loop.

Cheers,
Longman