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Re: [PATCH] Properly handle forced elision in pthread_mutex_trylock
- From: OndÅej BÃlka <neleai at seznam dot cz>
- To: Andreas Schwab <schwab at suse dot de>
- Cc: libc-alpha at sourceware dot org
- Date: Tue, 9 Dec 2014 23:07:29 +0100
- Subject: Re: [PATCH] Properly handle forced elision in pthread_mutex_trylock
- Authentication-results: sourceware.org; auth=none
- References: <mvmzjawx2w2 dot fsf at hawking dot suse dot de>
On Tue, Dec 09, 2014 at 04:24:13PM +0100, Andreas Schwab wrote:
> According to https://sourceware.org/bugzilla/show_bug.cgi?id=16657#c10
> this is the correct solution.
>
Should be ok as it was also acked by Andi in bugzilla, it would be
better if discussion was on mailing list.
> Andreas.
>
> [BZ #16657]
> * nptl/pthread_mutex_trylock.c (__pthread_mutex_trylock): Use
> FORCE_ELISION instead of DO_ELISION.
> * sysdeps/unix/sysv/linux/x86/force-elision.h (DO_ELISION):
> Remove.
> * sysdeps/unix/sysv/linux/s390/force-elision.h (DO_ELISION):
> Likewise.
> ---
> nptl/pthread_mutex_trylock.c | 10 +++-------
> sysdeps/unix/sysv/linux/s390/force-elision.h | 5 -----
> sysdeps/unix/sysv/linux/x86/force-elision.h | 5 -----
> 3 files changed, 3 insertions(+), 17 deletions(-)
>
> diff --git a/nptl/pthread_mutex_trylock.c b/nptl/pthread_mutex_trylock.c
> index 0293d0f..c4622aa 100644
> --- a/nptl/pthread_mutex_trylock.c
> +++ b/nptl/pthread_mutex_trylock.c
> @@ -26,13 +26,10 @@
> #define lll_trylock_elision(a,t) lll_trylock(a)
> #endif
>
> -#ifndef DO_ELISION
> -#define DO_ELISION(m) 0
> +#ifndef FORCE_ELISION
> +#define FORCE_ELISION(m, s)
> #endif
>
> -/* We don't force elision in trylock, because this can lead to inconsistent
> - lock state if the lock was actually busy. */
> -
> int
> __pthread_mutex_trylock (mutex)
> pthread_mutex_t *mutex;
> @@ -77,8 +74,7 @@ __pthread_mutex_trylock (mutex)
> return 0;
>
> case PTHREAD_MUTEX_TIMED_NP:
> - if (DO_ELISION (mutex))
> - goto elision;
> + FORCE_ELISION (mutex, goto elision);
> /*FALL THROUGH*/
> case PTHREAD_MUTEX_ADAPTIVE_NP:
> case PTHREAD_MUTEX_ERRORCHECK_NP:
> diff --git a/sysdeps/unix/sysv/linux/s390/force-elision.h b/sysdeps/unix/sysv/linux/s390/force-elision.h
> index 8fd7684..31b3662 100644
> --- a/sysdeps/unix/sysv/linux/s390/force-elision.h
> +++ b/sysdeps/unix/sysv/linux/s390/force-elision.h
> @@ -17,11 +17,6 @@
> <http://www.gnu.org/licenses/>. */
>
> #ifdef ENABLE_LOCK_ELISION
> -/* Check for elision on this lock without upgrading. */
> -#define DO_ELISION(m) \
> - (__pthread_force_elision \
> - && (m->__data.__kind & PTHREAD_MUTEX_NO_ELISION_NP) == 0) \
> -
> /* Automatically enable elision for existing user lock kinds. */
> #define FORCE_ELISION(m, s) \
> if (__pthread_force_elision \
> diff --git a/sysdeps/unix/sysv/linux/x86/force-elision.h b/sysdeps/unix/sysv/linux/x86/force-elision.h
> index 945f886..a767cf1 100644
> --- a/sysdeps/unix/sysv/linux/x86/force-elision.h
> +++ b/sysdeps/unix/sysv/linux/x86/force-elision.h
> @@ -16,11 +16,6 @@
> License along with the GNU C Library; if not, see
> <http://www.gnu.org/licenses/>. */
>
> -/* Check for elision on this lock without upgrading. */
> -#define DO_ELISION(m) \
> - (__pthread_force_elision \
> - && (m->__data.__kind & PTHREAD_MUTEX_NO_ELISION_NP) == 0) \
> -
> /* Automatically enable elision for existing user lock kinds. */
> #define FORCE_ELISION(m, s) \
> if (__pthread_force_elision \
> --
> 2.2.0
>