From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751558AbdB0OcM (ORCPT ); Mon, 27 Feb 2017 09:32:12 -0500 Received: from bh-25.webhostbox.net ([208.91.199.152]:35253 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751360AbdB0OcJ (ORCPT ); Mon, 27 Feb 2017 09:32:09 -0500 Subject: Re: watchdog: softdog: fire watchdog even if softirqs do not get to run To: Niklas Cassel References: <1487355902-28020-1-git-send-email-niklass@axis.com> <20170227040425.GA9023@roeck-us.net> Cc: wim@iguana.be, edumazet@google.com, peterz@infradead.org, linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org From: Guenter Roeck Message-ID: Date: Mon, 27 Feb 2017 06:31:12 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: linux@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: linux@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/27/2017 04:58 AM, Niklas Cassel wrote: > On 02/27/2017 05:04 AM, Guenter Roeck wrote: >> On Fri, Feb 17, 2017 at 07:25:02PM +0100, Niklas Cassel wrote: >>> From: Niklas Cassel >>> >>> Checking for timer expiration is done from the softirq TIMER_SOFTIRQ. >>> >>> Since commit 4cd13c21b207 ("softirq: Let ksoftirqd do its job"), >>> pending softirqs are no longer always handled immediately, instead, >>> if there are pending softirqs, and ksoftirqd is in state TASK_RUNNING, >>> the handling of the softirqs are deferred, and are instead supposed >>> to be handled by ksoftirqd, when ksoftirqd gets scheduled. >>> >>> If a user space process with a real-time policy starts to misbehave >>> by never relinquishing the CPU while ksoftirqd is in state TASK_RUNNING, >>> what will happen is that all softirqs will get deferred, while ksoftirqd, >>> which is supposed to handle the deferred softirqs, will never get to run. >>> >>> To make sure that the watchdog is able to fire even when we do not get >>> to run softirqs, replace the timers with hrtimers. >>> >>> Signed-off-by: Niklas Cassel >>> Reviewed-by: Guenter Roeck >> Niklas, >> >> Please rebase onto current mainline, test, and resubmit. > > I've sent out a v2 now :) > > Although, I thought that it was a bit weird that the conflicting patch > was in Linus tree but is not in next-20170227. > It was in the watchdog-next branch of my repository at kernel.org, which is not in -next. I'll have to sort that out with Wim at some point. > I'm not sure if you are the web master for www.linux-watchdog.org, > but their cgit seems to be broken: > http://www.linux-watchdog.org/cgi-bin/gitweb.cgi?p=linux-watchdog.git;a=summary > http://www.linux-watchdog.org/cgi-bin/gitweb.cgi?p=linux-watchdog-next.git;a=summary > Wim knows about it, and plans to replace the server. Guenter