[PATCH 2/2] kernel/smp: Use make csd_lock_wait be smp_cond_acquire

Davidlohr Bueso
2016-03-10T01:56:47Z

From: Davidlohr Bueso <dave@stgolabs>

We can micro-optimize this call and mildly relax the
barrier requirements by relying on ctrl + rmb, keeping
the acquire semantics. In addition, this is pretty much
the now standard for busy-waiting under such restraints.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
kernel/smp.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index c91e00178f8f..74165443c240 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -107,8 +107,7 @@ void __init call_function_init(void)
*/
static __always_inline void csd_lock_wait(struct call_single_data *csd)
{
- while (smp_load_acquire(&csd->flags) & CSD_FLAG_LOCK)
- cpu_relax();
+ smp_cond_acquire(!(csd->flags & CSD_FLAG_LOCK));
}

static __always_inline void csd_lock(struct call_single_data *csd)
--
2.1.4