[tip:sched/core] sched/deadline: Remove cpu_active_mask from cpudl_find()

[tip-bot for Xunlei Pang <tipbot@zytor.com>]

Commit-ID:  9659e1eeee28f7025b6545934d644d19e9c6e603
Gitweb:     http://git.kernel.org/tip/9659e1eeee28f7025b6545934d644d19e9c6e603
Author:     Xunlei Pang <pang.xunlei@linaro.org>
AuthorDate: Mon, 19 Jan 2015 04:49:37 +0000
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 4 Feb 2015 07:52:29 +0100

sched/deadline: Remove cpu_active_mask from cpudl_find()

cpu_active_mask is rarely changed (only on hotplug), so remove this
operation to gain a little performance.

If there is a change in cpu_active_mask, rq_online_dl() and
rq_offline_dl() should take care of it normally, so cpudl::free_cpus
carries enough information for us.

For the rare case when a task is put onto a dying cpu (which
rq_offline_dl() can't handle in a timely fashion), it will be
handled through _cpu_down()->...->multi_cpu_stop()->migration_call()
->migrate_tasks(), preventing the task from hanging on the
dead cpu.

Cc: Juri Lelli <juri.lelli@gmail.com>
Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
[peterz: changelog]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1421642980-10045-2-git-send-email-pang.xunlei@linaro.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/cpudeadline.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index fd9d3fb..c6acb07 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -108,8 +108,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
 	const struct sched_dl_entity *dl_se = &p->dl;
 
 	if (later_mask &&
-	    cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed) &&
-	    cpumask_and(later_mask, later_mask, cpu_active_mask)) {
+	    cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
 		best_cpu = cpumask_any(later_mask);
 		goto out;
 	} else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&