linux-kernel - [RFC PATCH nohz] return NOTIFY_BAD in cpu down call back to stop offlining the cpu

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Message-ID: <1368780244.2813.14.camel@ThinkPad-T5421>
Date:	Fri, 17 May 2013 16:44:04 +0800
From:	Li Zhong <zhong@...ux.vnet.ibm.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>
Subject: [RFC PATCH nohz] return NOTIFY_BAD in cpu down call back to stop
 offlining the cpu

In tick_nohz_cpu_down_callback() if the cpu is the one handling
timekeeping , it seems that we should return something that could stop
notify CPU_DOWN_PREPARE, and then start notify CPU_DOWN_FAILED on the
already called notifier call backs.

-EINVAL will be converted to 0 by notifier_to_errno(), then the cpu
would be taken down with part of the DOWN_PREPARE notifier callbacks
called, and something bad could happen after that.

Signed-off-by: Li Zhong <zhong@...ux.vnet.ibm.com>
---
 kernel/time/tick-sched.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index bc67d42..17b8155 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -306,7 +306,7 @@ static int __cpuinit tick_nohz_cpu_down_callback(struct notifier_block *nfb,
 		 * we can't safely shutdown that CPU.
 		 */
 		if (have_nohz_full_mask && tick_do_timer_cpu == cpu)
-			return -EINVAL;
+			return NOTIFY_BAD;
 		break;
 	}
 	return NOTIFY_OK;
-- 
1.7.1

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