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Subject[PATCH] kthread_bind: don't wait in kthread_bind for presmp initcalls
Date
From: Abbas Raza <Abbas_Raza@mentor.com>

wait_task_inactive shouldn't be called in __kthread_bind for presmp
initcalls the same way it is done in !SMP case.

more info here:
http://permalink.gmane.org/gmane.linux.kernel.embedded/4046

This patch improves boot time for pre-smp initcalls as given below

boot time with this patch:

calling spawn_ksoftirqd+0x0/0x30 @ 1
initcall spawn_ksoftirqd+0x0/0x30 returned 0 after 0 usecs

boot time without this patch:

calling spawn_ksoftirqd+0x0/0x30 @ 1
initcall spawn_ksoftirqd+0x0/0x30 returned 0 after 19531 usecs

Signed-off-by: Abbas Raza <Abbas_Raza@mentor.com>
---
kernel/kthread.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 760e86d..28b5c4b 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -290,11 +290,17 @@ EXPORT_SYMBOL(kthread_create_on_node);

static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
{
- /* Must have done schedule() in kthread() before we set_task_cpu */
- if (!wait_task_inactive(p, state)) {
- WARN_ON(1);
- return;
+ if (!((num_online_cpus() == 1) && !cpu)) {
+ /*
+ * Must have done schedule() in kthread() before
+ * we set_task_cpu
+ */
+ if (!wait_task_inactive(p, state)) {
+ WARN_ON(1);
+ return;
+ }
}
+
/* It's safe because the task is inactive. */
do_set_cpus_allowed(p, cpumask_of(cpu));
p->flags |= PF_NO_SETAFFINITY;
--
1.8.3.2


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