path: root/kernel
diff options
authorPeter Boonstoppel <>2012-07-19 14:58:10 -0700
committerSimone Willett <>2012-07-31 14:58:16 -0700
commit3e34666ada220c17362c25e0c19d2319db449662 (patch)
tree9be22a2b641eb524ef1e9064e9652932dfd5a693 /kernel
parent6308fd8ea1d7291835b3b689779a5b58ac0cf47a (diff)
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 <>
Diffstat (limited to 'kernel')
1 files changed, 11 insertions, 0 deletions
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 <linux/mutex.h>
#include <linux/slab.h>
#include <linux/freezer.h>
+#include <linux/preempt.h>
#include <trace/events/sched.h>
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 */
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();
+ preempt_enable_no_resched();
ret = -EINTR;