Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752394Ab3ETKMn (ORCPT ); Mon, 20 May 2013 06:12:43 -0400 Received: from mail-la0-f43.google.com ([209.85.215.43]:63188 "EHLO mail-la0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751332Ab3ETKMm (ORCPT ); Mon, 20 May 2013 06:12:42 -0400 MIME-Version: 1.0 In-Reply-To: <5199F1E9.2080002@linux.vnet.ibm.com> References: <1368780244.2813.14.camel@ThinkPad-T5421> <5199F1E9.2080002@linux.vnet.ibm.com> Date: Mon, 20 May 2013 12:12:40 +0200 Message-ID: Subject: Re: [RFC PATCH nohz] return NOTIFY_BAD in cpu down call back to stop offlining the cpu From: Frederic Weisbecker To: "Srivatsa S. Bhat" Cc: Li Zhong , LKML Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1931 Lines: 54 2013/5/20 Srivatsa S. Bhat : > On 05/17/2013 02:14 PM, Li Zhong wrote: >> 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(), > > This above line is not relevant here, because notifier_call_chain() > doesn't use notifier_to/from_errno(). It simply uses a straight-forward > check like this: > > if ((ret & NOTIFY_STOP_MASK) == NOTIFY_STOP_MASK) > break; > >> 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 >> --- > > Reviewed-by: Srivatsa S. Bhat I applied the patch and will send to Ingo, thanks guys! > >> 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; >> > > Regards, > Srivatsa S. Bhat > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/