[PATCH] cpuset semaphore depth check optimize
Optimize the deadlock avoidance check on the global cpuset
semaphore cpuset_sem. Instead of adding a depth counter to the
task struct of each task, rather just two words are enough, one
to store the depth and the other the current cpuset_sem holder.
Thanks to Nikita Danilov for the idea.
Signed-off-by: Paul Jackson <pj@sgi.com>
[ We may want to change this further, but at least it's now
a totally internal decision to the cpusets code ]
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 407b5f0..79866bc 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -180,6 +180,8 @@
*/
static DECLARE_MUTEX(cpuset_sem);
+static struct task_struct *cpuset_sem_owner;
+static int cpuset_sem_depth;
/*
* The global cpuset semaphore cpuset_sem can be needed by the
@@ -200,16 +202,19 @@
static inline void cpuset_down(struct semaphore *psem)
{
- if (current->cpuset_sem_nest_depth == 0)
+ if (cpuset_sem_owner != current) {
down(psem);
- current->cpuset_sem_nest_depth++;
+ cpuset_sem_owner = current;
+ }
+ cpuset_sem_depth++;
}
static inline void cpuset_up(struct semaphore *psem)
{
- current->cpuset_sem_nest_depth--;
- if (current->cpuset_sem_nest_depth == 0)
+ if (--cpuset_sem_depth == 0) {
+ cpuset_sem_owner = NULL;
up(psem);
+ }
}
/*