Use rcu_read_lock_sched / rcu_read_unlock_sched / synchronize_sched
instead of rcu_read_lock / rcu_read_unlock / synchronize_rcu.
This is an optimization. The RCU-protected region is very small, so
there will be no latency problems if we disable preempt in this region.
So we use rcu_read_lock_sched / rcu_read_unlock_sched that translates
to preempt_disable / preempt_disable. It is smaller (and supposedly
faster) than preemptible rcu_read_lock / rcu_read_unlock.
Signed-off-by: Mikulas Patocka <mpato...@redhat.com>
---
include/linux/percpu-rwsem.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
Index: linux-3.6.3-fast/include/linux/percpu-rwsem.h
===================================================================
--- linux-3.6.3-fast.orig/include/linux/percpu-rwsem.h 2012-10-23
01:21:49.000000000 +0200
+++ linux-3.6.3-fast/include/linux/percpu-rwsem.h 2012-10-23
01:36:23.000000000 +0200
@@ -17,16 +17,16 @@ struct percpu_rw_semaphore {
static inline void percpu_down_read(struct percpu_rw_semaphore *p)
{
- rcu_read_lock();
+ rcu_read_lock_sched();
if (unlikely(p->locked)) {
- rcu_read_unlock();
+ rcu_read_unlock_sched();
mutex_lock(&p->mtx);
this_cpu_inc(*p->counters);
mutex_unlock(&p->mtx);
return;
}
this_cpu_inc(*p->counters);
- rcu_read_unlock();
+ rcu_read_unlock_sched();
light_mb(); /* A, between read of p->locked and read of data, paired
with D */
}
@@ -51,7 +51,7 @@ static inline void percpu_down_write(str
{
mutex_lock(&p->mtx);
p->locked = true;
- synchronize_rcu();
+ synchronize_sched(); /* make sure that all readers exit the
rcu_read_lock_sched region */
while (__percpu_count(p->counters))
msleep(1);
heavy_mb(); /* C, between read of p->counter and write to data, paired
with B */
--
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