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[PATCH] cpuset semaphore depth check optimize

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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 <[email protected]>

[ 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 <[email protected]>
This commit is contained in:
Paul Jackson 2005-09-12 04:30:30 -07:00 • committed by Linus Torvalds
commit b3426599af
2 changed files with 9 additions and 5 deletions
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13
kernel/cpuset.c
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@ -180,6 +180,8 @@ static struct super_block *cpuset_sb = NULL;
*/
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 DECLARE_MUTEX(cpuset_sem);
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);
}
}
/*