migrate_timers: add comment, use spinlock_irq()
Add the comment to explain why the double lock in migrate_timers()
can't deadlock.
Change the code to use spinlock_irq() instead of local_irq_disable()
+ spin_lock().
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index b8e4dce..03ea137 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1620,9 +1620,11 @@
new_base = &get_cpu_var(hrtimer_bases);
tick_cancel_sched_timer(cpu);
-
- local_irq_disable();
- spin_lock(&new_base->lock);
+ /*
+ * The caller is globally serialized and nobody else
+ * takes two locks at once, deadlock is not possible.
+ */
+ spin_lock_irq(&new_base->lock);
spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
@@ -1631,8 +1633,7 @@
}
spin_unlock(&old_base->lock);
- spin_unlock(&new_base->lock);
- local_irq_enable();
+ spin_unlock_irq(&new_base->lock);
put_cpu_var(hrtimer_bases);
}
#endif /* CONFIG_HOTPLUG_CPU */