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 <pboonstop...@nvidia.com> --- kernel/kthread.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index b579af5..f681b14 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -16,6 +16,8 @@ #include <linux/mutex.h> #include <linux/slab.h> #include <linux/freezer.h> +#include <linux/preempt.h> +#include <linux/thread_info.h> #include <trace/events/sched.h> static DEFINE_SPINLOCK(kthread_create_lock); @@ -113,7 +115,10 @@ static int kthread(void *_create) /* OK, tell user we're spawned, wait for stop or wakeup */ __set_current_state(TASK_UNINTERRUPTIBLE); create->result = current; + preempt_disable(); complete(&create->done); + clear_need_resched(); + preempt_enable_no_resched(); schedule(); ret = -EINTR; -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/