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