Re: [PATCH] Use C11 atomics instead of atomic_and/or

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

On 05/09/22 13:48, Wilco Dijkstra wrote:
> Remove the 4 uses of atomic_and and atomic_or with atomic_fetch_and_acquire and
> atomic_fetch_or_acquire
> 
> Passes regress on AArch64.

LGTM, the current atomic_or and atomic_and have acquire semantic already.  What
I am not not sure if if we need to use release MO on start_thread, since the
idea is to synchronize with the locking on pthread_mutex_lock.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> 
> ---
> 
> diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
> index d206ed7bf4c2305c0d65bc2a47baefe02969e3d2..d802c67b059af390e122e82f09e886d0c8950fd7 100644
> --- a/nptl/pthread_create.c
> +++ b/nptl/pthread_create.c
> @@ -539,7 +539,7 @@ start_thread (void *arg)
>  # endif
>  	  this->__list.__next = NULL;
>  
> -	  atomic_or (&this->__lock, FUTEX_OWNER_DIED);
> +	  atomic_fetch_or_acquire (&this->__lock, FUTEX_OWNER_DIED);
>  	  futex_wake ((unsigned int *) &this->__lock, 1,
>  		      /* XYZ */ FUTEX_SHARED);
>  	}
> diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
> index 6e767a87247063c0ac84242ef13e72af79021104..439b1e6391c50d5922dec6c48e7f2a2a632a89d9 100644
> --- a/nptl/pthread_mutex_lock.c
> +++ b/nptl/pthread_mutex_lock.c
> @@ -462,7 +462,7 @@ __pthread_mutex_lock_full (pthread_mutex_t *mutex)
>  
>  	if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED))
>  	  {
> -	    atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
> +	    atomic_fetch_and_acquire (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
>  
>  	    /* We got the mutex.  */
>  	    mutex->__data.__count = 1;
> diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
> index 0fcaabfb482546fd6f1f9cc4b13edc82f6e6796c..af70a60528cb101c8e52d4165950ee0d11f6f895 100644
> --- a/nptl/pthread_mutex_timedlock.c
> +++ b/nptl/pthread_mutex_timedlock.c
> @@ -392,7 +392,7 @@ __pthread_mutex_clocklock_common (pthread_mutex_t *mutex,
>  
>  	if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED))
>  	  {
> -	    atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
> +	    atomic_fetch_and_acquire (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
>  
>  	    /* We got the mutex.  */
>  	    mutex->__data.__count = 1;
> diff --git a/nptl/pthread_mutex_trylock.c b/nptl/pthread_mutex_trylock.c
> index 8a7de8e598803f606899fe1c9b8775bc24dd14ec..50524942a76c753ce4add20c35dfe7f659a1908b 100644
> --- a/nptl/pthread_mutex_trylock.c
> +++ b/nptl/pthread_mutex_trylock.c
> @@ -308,7 +308,7 @@ ___pthread_mutex_trylock (pthread_mutex_t *mutex)
>  
>  	if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED))
>  	  {
> -	    atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
> +	    atomic_fetch_and_acquire (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
>  
>  	    /* We got the mutex.  */
>  	    mutex->__data.__count = 1;
>