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authorCheng Chao <cs.os.kernel@gmail.com>2016-09-14 05:01:50 +0300
committerIngo Molnar <mingo@kernel.org>2016-09-22 15:53:45 +0300
commitbf89a304722f6904009499a31dc68ab9a5c9742e (patch)
tree2177d0136fa62ca04091b6f5823ad32b055bbf7c /kernel/stop_machine.c
parent0b8473570ce1af3e80da05b59f9321f30253de4d (diff)
downloadlinux-bf89a304722f6904009499a31dc68ab9a5c9742e.tar.xz
stop_machine: Avoid a sleep and wakeup in stop_one_cpu()
In case @cpu == smp_proccessor_id(), we can avoid a sleep+wakeup cycle by doing a preemption. Callers such as sched_exec() can benefit from this change. Signed-off-by: Cheng Chao <cs.os.kernel@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: akpm@linux-foundation.org Cc: chris@chris-wilson.co.uk Cc: tj@kernel.org Link: http://lkml.kernel.org/r/1473818510-6779-1-git-send-email-cs.os.kernel@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/stop_machine.c')
-rw-r--r--kernel/stop_machine.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 4a1ca5f6da7e..082e71f17a58 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -126,6 +126,11 @@ int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
cpu_stop_init_done(&done, 1);
if (!cpu_stop_queue_work(cpu, &work))
return -ENOENT;
+ /*
+ * In case @cpu == smp_proccessor_id() we can avoid a sleep+wakeup
+ * cycle by doing a preemption:
+ */
+ cond_resched();
wait_for_completion(&done.completion);
return done.ret;
}