From df3a4e104fb63f96f05b29931dd83e272c2b7936 Mon Sep 17 00:00:00 2001 From: Stefan Liebler Date: Mon, 6 Feb 2017 13:44:23 +0100 Subject: Add __glibc_unlikely hint in lll_trylock, lll_cond_trylock. The macros lll_trylock, lll_cond_trylock are extended by an __glibc_unlikely hint. Now the trylock macros are based on the same assumption about a free/busy lock as lll_lock. With the hint gcc emits code in e.g. pthread_mutex_trylock which does not use jumps if the lock is free. Without the hint it had to jump away if the lock is free. Tested on s390x, ppc. ChangeLog: * sysdeps/nptl/lowlevellock.h (lll_trylock, lll_cond_trylock): Add __glibc_unlikely hint. --- ChangeLog | 5 +++++ sysdeps/nptl/lowlevellock.h | 4 ++-- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/ChangeLog b/ChangeLog index dd0a0b5..e4885cf 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,8 @@ +2017-02-06 Stefan Liebler + + * sysdeps/nptl/lowlevellock.h (lll_trylock, lll_cond_trylock): + Add __glibc_unlikely hint. + 2017-02-06 Adhemerval Zanella [BZ #16640] diff --git a/sysdeps/nptl/lowlevellock.h b/sysdeps/nptl/lowlevellock.h index 42d9658..54e3c28 100644 --- a/sysdeps/nptl/lowlevellock.h +++ b/sysdeps/nptl/lowlevellock.h @@ -64,13 +64,13 @@ 0. Otherwise leave lock unchanged and return non-zero to indicate that the lock was not acquired. */ #define lll_trylock(lock) \ - atomic_compare_and_exchange_bool_acq (&(lock), 1, 0) + __glibc_unlikely (atomic_compare_and_exchange_bool_acq (&(lock), 1, 0)) /* If LOCK is 0 (not acquired), set to 2 (acquired, possibly with waiters) and return 0. Otherwise leave lock unchanged and return non-zero to indicate that the lock was not acquired. */ #define lll_cond_trylock(lock) \ - atomic_compare_and_exchange_bool_acq (&(lock), 2, 0) + __glibc_unlikely (atomic_compare_and_exchange_bool_acq (&(lock), 2, 0)) extern void __lll_lock_wait_private (int *futex) attribute_hidden; extern void __lll_lock_wait (int *futex, int private) attribute_hidden; -- cgit v1.1