diff options
| author | Waiman Long <longman@redhat.com> | 2019-04-04 13:43:13 -0400 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2019-04-10 10:56:01 +0200 |
| commit | a338ecb07a338c9a8b0ca0010e862ebe598b1551 (patch) | |
| tree | 8dae984357ba838cd16a28c8dbc099edf0ebd473 /kernel/locking | |
| parent | 12a30a7fc142a123c61da9623bd824d95d36c12e (diff) | |
locking/rwsem: Micro-optimize rwsem_try_read_lock_unqueued()
The atomic_long_cmpxchg_acquire() in rwsem_try_read_lock_unqueued() is
replaced by atomic_long_try_cmpxchg_acquire() to simpify the code and
generate slightly better assembly code.
There is no functional change.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-5-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/locking')
| -rw-r--r-- | kernel/locking/rwsem-xadd.c | 15 |
1 files changed, 5 insertions, 10 deletions
diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index c213869e1aa7..f6198e1a58f6 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -259,21 +259,16 @@ static inline bool rwsem_try_write_lock(long count, struct rw_semaphore *sem) */ static inline bool rwsem_try_write_lock_unqueued(struct rw_semaphore *sem) { - long old, count = atomic_long_read(&sem->count); + long count = atomic_long_read(&sem->count); - while (true) { - if (!(count == 0 || count == RWSEM_WAITING_BIAS)) - return false; - - old = atomic_long_cmpxchg_acquire(&sem->count, count, - count + RWSEM_ACTIVE_WRITE_BIAS); - if (old == count) { + while (!count || count == RWSEM_WAITING_BIAS) { + if (atomic_long_try_cmpxchg_acquire(&sem->count, &count, + count + RWSEM_ACTIVE_WRITE_BIAS)) { rwsem_set_owner(sem); return true; } - - count = old; } + return false; } static inline bool owner_on_cpu(struct task_struct *owner) |