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/timer.c b/kernel/timer.c
index 03bc7f1..e8019cc 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1435,9 +1435,11 @@
BUG_ON(cpu_online(cpu));
old_base = per_cpu(tvec_bases, cpu);
new_base = get_cpu_var(tvec_bases);
-
- 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);
BUG_ON(old_base->running_timer);
@@ -1452,8 +1454,7 @@
}
spin_unlock(&old_base->lock);
- spin_unlock(&new_base->lock);
- local_irq_enable();
+ spin_unlock_irq(&new_base->lock);
put_cpu_var(tvec_bases);
}
#endif /* CONFIG_HOTPLUG_CPU */
