From 3e34666ada220c17362c25e0c19d2319db449662 Mon Sep 17 00:00:00 2001 From: Peter Boonstoppel Date: Thu, 19 Jul 2012 14:58:10 -0700 Subject: kthread: disable preemption during complete() After a kthread is created it signals the requester using complete() and enters TASK_UNINTERRUPTIBLE. However, since complete() wakes up the requesting thread this can cause a preemption. The preemption will not remove the task from the runqueue (for that schedule() has to be invoked directly). This is a problem if directly after kthread creation you try to do a kthread_bind(), which will block in HZ steps until the thread is off the runqueue. This patch disables preemption during complete(), since we call schedule() directly afterwards, so it will correctly enter TASK_UNINTERRUPTIBLE. This speeds up kthread creation/binding during cpu hotplug significantly. Change-Id: I856ddd4e01ebdb198ba90f343b4a0c5933fd2b23 Signed-off-by: Peter Boonstoppel --- kernel/kthread.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'kernel') diff --git a/kernel/kthread.c b/kernel/kthread.c index 4ba7cccb4994..390ef119aa50 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -16,6 +16,7 @@ #include #include #include +#include #include static DEFINE_SPINLOCK(kthread_create_lock); @@ -88,7 +89,17 @@ static int kthread(void *_create) /* OK, tell user we're spawned, wait for stop or wakeup */ __set_current_state(TASK_UNINTERRUPTIBLE); create->result = current; + + /* + * Disable preemption so we enter TASK_UNINTERRUPTIBLE after + * complete() instead of possibly being preempted. This speeds + * up clients that do a kthread_bind() directly after + * creation. + */ + preempt_disable(); complete(&create->done); + preempt_enable_no_resched(); + schedule(); ret = -EINTR; -- cgit v1.2.3