diff options
| author | Martin Pieuchot <mpi@cvs.openbsd.org> | 2017-10-12 09:19:46 +0000 |
|---|---|---|
| committer | Martin Pieuchot <mpi@cvs.openbsd.org> | 2017-10-12 09:19:46 +0000 |
| commit | b477515867e7e65944261e4034d7952fec5ab513 (patch) | |
| tree | 223548cd2fbb5b2d401ec17b54227932f665a9c3 /sys/kern | |
| parent | ed871f5e0c4abb0cd4cc968ba206117a33ff83e2 (diff) | |
Use a temporary variable in rw_status() to dereference only once the
volatile member of the struct.
Not forcing a memory read on every access, 3 in this function, might
reduce cache traffic in some cases.
Micro-optimization and diff provided by Mateusz Guzik.
ok visa@
Diffstat (limited to 'sys/kern')
| -rw-r--r-- | sys/kern/kern_rwlock.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/sys/kern/kern_rwlock.c b/sys/kern/kern_rwlock.c index e2c3caed0ab..9252413b1b3 100644 --- a/sys/kern/kern_rwlock.c +++ b/sys/kern/kern_rwlock.c @@ -1,4 +1,4 @@ -/* $OpenBSD: kern_rwlock.c,v 1.30 2017/08/12 23:27:44 guenther Exp $ */ +/* $OpenBSD: kern_rwlock.c,v 1.31 2017/10/12 09:19:45 mpi Exp $ */ /* * Copyright (c) 2002, 2003 Artur Grabowski <art@openbsd.org> @@ -312,13 +312,15 @@ _rw_exit(struct rwlock *rwl LOCK_FL_VARS) int rw_status(struct rwlock *rwl) { - if (rwl->rwl_owner & RWLOCK_WRLOCK) { - if (RW_PROC(curproc) == RW_PROC(rwl->rwl_owner)) + unsigned long owner = rwl->rwl_owner; + + if (owner & RWLOCK_WRLOCK) { + if (RW_PROC(curproc) == RW_PROC(owner)) return RW_WRITE; else return RW_WRITE_OTHER; } - if (rwl->rwl_owner) + if (owner) return RW_READ; return (0); } |