From 9f3520c3115b451ac1301779fc3c769d94907a70 Mon Sep 17 00:00:00 2001 From: Yuanhan Liu Date: Fri, 8 May 2015 18:19:05 +1000 Subject: wait: introduce wait_event_exclusive_cmd It's just a variant of wait_event_cmd(), with exclusive flag being set. For cases like RAID5, which puts many processes to sleep until 1/4 resources are free, a wake_up wakes up all processes to run, but there is one process being able to get the resource as it's protected by a spin lock. That ends up introducing heavy lock contentions, and hurts performance badly. Here introduce wait_event_exclusive_cmd to relieve the lock contention naturally by letting wake_up just wake up one process. Cc: Ingo Molnar Cc: Peter Zijlstra v2: its assumed that wait*() and __wait*() have the same arguments - peterz Acked-by: Peter Zijlstra (Intel) Signed-off-by: Yuanhan Liu Signed-off-by: NeilBrown --- include/linux/wait.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'include/linux/wait.h') diff --git a/include/linux/wait.h b/include/linux/wait.h index 2db83349865b..db78c7204947 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -358,6 +358,19 @@ do { \ __ret; \ }) +#define __wait_event_exclusive_cmd(wq, condition, cmd1, cmd2) \ + (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 1, 0, \ + cmd1; schedule(); cmd2) +/* + * Just like wait_event_cmd(), except it sets exclusive flag + */ +#define wait_event_exclusive_cmd(wq, condition, cmd1, cmd2) \ +do { \ + if (condition) \ + break; \ + __wait_event_exclusive_cmd(wq, condition, cmd1, cmd2); \ +} while (0) + #define __wait_event_cmd(wq, condition, cmd1, cmd2) \ (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0, \ cmd1; schedule(); cmd2) -- cgit