diff options
| author | Martin Pieuchot <mpi@cvs.openbsd.org> | 2017-10-24 08:53:16 +0000 |
|---|---|---|
| committer | Martin Pieuchot <mpi@cvs.openbsd.org> | 2017-10-24 08:53:16 +0000 |
| commit | 1e0f3ecacdd43839fb71c03b5797317c4cd9701d (patch) | |
| tree | c77e5c406c7ed54e64aa93decc9172f43b90a409 | |
| parent | 7bf457912b08c92454707838773e51f0ba537965 (diff) | |
Use membar_enter_after_atomic(9) amd membar_exit_before_atomic(9).
Micro-optimization useful to x86 archs where the cmpxchg{q,l} instruction
used by rw_enter(9) and rw_exit(9) already include an implicit memory
barrier.
From Mateusz Guzik, ok visa@, mikeb@, kettenis@
| -rw-r--r-- | sys/kern/kern_rwlock.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/sys/kern/kern_rwlock.c b/sys/kern/kern_rwlock.c index 9252413b1b3..399c352f396 100644 --- a/sys/kern/kern_rwlock.c +++ b/sys/kern/kern_rwlock.c @@ -1,4 +1,4 @@ -/* $OpenBSD: kern_rwlock.c,v 1.31 2017/10/12 09:19:45 mpi Exp $ */ +/* $OpenBSD: kern_rwlock.c,v 1.32 2017/10/24 08:53:15 mpi Exp $ */ /* * Copyright (c) 2002, 2003 Artur Grabowski <art@openbsd.org> @@ -96,7 +96,7 @@ _rw_enter_read(struct rwlock *rwl LOCK_FL_VARS) rw_cas(&rwl->rwl_owner, owner, owner + RWLOCK_READ_INCR))) _rw_enter(rwl, RW_READ LOCK_FL_ARGS); else { - membar_enter(); + membar_enter_after_atomic(); WITNESS_CHECKORDER(&rwl->rwl_lock_obj, LOP_NEWORDER, file, line, NULL); WITNESS_LOCK(&rwl->rwl_lock_obj, 0, file, line); @@ -112,7 +112,7 @@ _rw_enter_write(struct rwlock *rwl LOCK_FL_VARS) RW_PROC(p) | RWLOCK_WRLOCK))) _rw_enter(rwl, RW_WRITE LOCK_FL_ARGS); else { - membar_enter(); + membar_enter_after_atomic(); WITNESS_CHECKORDER(&rwl->rwl_lock_obj, LOP_EXCLUSIVE | LOP_NEWORDER, file, line, NULL); WITNESS_LOCK(&rwl->rwl_lock_obj, LOP_EXCLUSIVE, file, line); @@ -126,7 +126,7 @@ _rw_exit_read(struct rwlock *rwl LOCK_FL_VARS) rw_assert_rdlock(rwl); - membar_exit(); + membar_exit_before_atomic(); if (__predict_false((owner & RWLOCK_WAIT) || rw_cas(&rwl->rwl_owner, owner, owner - RWLOCK_READ_INCR))) _rw_exit(rwl LOCK_FL_ARGS); @@ -141,7 +141,7 @@ _rw_exit_write(struct rwlock *rwl LOCK_FL_VARS) rw_assert_wrlock(rwl); - membar_exit(); + membar_exit_before_atomic(); if (__predict_false((owner & RWLOCK_WAIT) || rw_cas(&rwl->rwl_owner, owner, 0))) _rw_exit(rwl LOCK_FL_ARGS); @@ -261,7 +261,7 @@ retry: if (__predict_false(rw_cas(&rwl->rwl_owner, o, o + inc))) goto retry; - membar_enter(); + membar_enter_after_atomic(); /* * If old lock had RWLOCK_WAIT and RWLOCK_WRLOCK set, it means we @@ -295,7 +295,7 @@ _rw_exit(struct rwlock *rwl LOCK_FL_VARS) WITNESS_UNLOCK(&rwl->rwl_lock_obj, wrlock ? LOP_EXCLUSIVE : 0, file, line); - membar_exit(); + membar_exit_before_atomic(); do { owner = rwl->rwl_owner; if (wrlock) |