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Subject[tip:sched/urgent] sched_rt: don't allocate cpumask in fastpath
Commit-ID:  13b8bd0a5713bdf05659019badd7c0407984ece1
Gitweb: http://git.kernel.org/tip/13b8bd0a5713bdf05659019badd7c0407984ece1
Author: Rusty Russell <rusty@rustcorp.com.au>
AuthorDate: Wed, 25 Mar 2009 15:01:22 +1030
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 1 Apr 2009 13:24:51 +0200

sched_rt: don't allocate cpumask in fastpath

Impact: cleanup

As pointed out by Steven Rostedt. Since the arg in question is
unused, we simply change cpupri_find() to accept NULL.

Reported-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
LKML-Reference: <200903251501.22664.rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
kernel/sched_cpupri.c | 5 +++--
kernel/sched_rt.c | 15 ++++-----------
2 files changed, 7 insertions(+), 13 deletions(-)
diff --git a/kernel/sched_cpupri.c b/kernel/sched_cpupri.c
index 1e00bfa..cdd3c89 100644
--- a/kernel/sched_cpupri.c
+++ b/kernel/sched_cpupri.c
@@ -55,7 +55,7 @@ static int convert_prio(int prio)
* cpupri_find - find the best (lowest-pri) CPU in the system
* @cp: The cpupri context
* @p: The task
- * @lowest_mask: A mask to fill in with selected CPUs
+ * @lowest_mask: A mask to fill in with selected CPUs (or NULL)
*
* Note: This function returns the recommended CPUs as calculated during the
* current invokation. By the time the call returns, the CPUs may have in
@@ -81,7 +81,8 @@ int cpupri_find(struct cpupri *cp, struct task_struct *p,
if (cpumask_any_and(&p->cpus_allowed, vec->mask) >= nr_cpu_ids)
continue;

- cpumask_and(lowest_mask, &p->cpus_allowed, vec->mask);
+ if (lowest_mask)
+ cpumask_and(lowest_mask, &p->cpus_allowed, vec->mask);
return 1;
}

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index bac1061..fbec5a5 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -805,20 +805,15 @@ static int select_task_rq_rt(struct task_struct *p, int sync)

static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
{
- cpumask_var_t mask;
-
if (rq->curr->rt.nr_cpus_allowed == 1)
return;

- if (!alloc_cpumask_var(&mask, GFP_ATOMIC))
- return;
-
if (p->rt.nr_cpus_allowed != 1
- && cpupri_find(&rq->rd->cpupri, p, mask))
- goto free;
+ && cpupri_find(&rq->rd->cpupri, p, NULL))
+ return;

- if (!cpupri_find(&rq->rd->cpupri, rq->curr, mask))
- goto free;
+ if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
+ return;

/*
* There appears to be other cpus that can accept
@@ -827,8 +822,6 @@ static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
*/
requeue_task_rt(rq, p, 1);
resched_task(rq->curr);
-free:
- free_cpumask_var(mask);
}

#endif /* CONFIG_SMP */

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