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| author | Mikulas Patocka <mpatocka@redhat.com> | 2012-10-22 19:39:16 -0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-10-28 10:59:36 -0700 |
| commit | 1bf11c53535ab87e3bf14ecdf6747bf46f601c5d (patch) | |
| tree | 9170fa956be0f564b988a88685eb82584347c2cf /include | |
| parent | 5c1eabe68501d1e1b1586c7f4c46cc531828c4ab (diff) | |
| download | lwn-1bf11c53535ab87e3bf14ecdf6747bf46f601c5d.tar.gz lwn-1bf11c53535ab87e3bf14ecdf6747bf46f601c5d.zip | |
percpu-rw-semaphores: use rcu_read_lock_sched
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 <mpatocka@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/percpu-rwsem.h | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h index 18f35b54286c..250a4acddb2b 100644 --- a/include/linux/percpu-rwsem.h +++ b/include/linux/percpu-rwsem.h @@ -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(struct percpu_rw_semaphore *p) { 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 */ |