From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by aws-us-west-2-korg-lkml-1.web.codeaurora.org (Postfix) with ESMTP id B3672C433EF for ; Tue, 12 Jun 2018 00:45:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 49B94208AF for ; Tue, 12 Jun 2018 00:45:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 49B94208AF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xmission.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933819AbeFLApU convert rfc822-to-8bit (ORCPT ); Mon, 11 Jun 2018 20:45:20 -0400 Received: from out03.mta.xmission.com ([166.70.13.233]:56530 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932893AbeFLApS (ORCPT ); Mon, 11 Jun 2018 20:45:18 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]) by out03.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1fSXQz-0005s5-Pg; Mon, 11 Jun 2018 18:45:17 -0600 Received: from 97-119-124-205.omah.qwest.net ([97.119.124.205] helo=x220.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1fSXQz-0005QE-7j; Mon, 11 Jun 2018 18:45:17 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: "Farnitano\, Jarrett" Cc: "kexec\@lists.infradead.org" , "linux-kernel\@vger.kernel.org" References: <1528738546-3328-1-git-send-email-jmf@amazon.com> <87po0xszdx.fsf@xmission.com> <588FC7E2-C106-456A-81E7-A98F99F0E392@amazon.com> Date: Mon, 11 Jun 2018 19:45:11 -0500 In-Reply-To: <588FC7E2-C106-456A-81E7-A98F99F0E392@amazon.com> (Jarrett Farnitano's message of "Mon, 11 Jun 2018 23:47:46 +0000") Message-ID: <87bmcgsui0.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-XM-SPF: eid=1fSXQz-0005QE-7j;;;mid=<87bmcgsui0.fsf@xmission.com>;;;hst=in02.mta.xmission.com;;;ip=97.119.124.205;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18kVqlagV0to1WidfJX5TdbnyQ3HBk29vU= X-SA-Exim-Connect-IP: 97.119.124.205 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH] kexec: yield to scheduler when loading kimage segments X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Farnitano, Jarrett" writes: >> On 6/11/18, 4:00 PM, "Eric W. Biederman" wrote: >> >> Is there a practical problem with unresponsiveness? You are talking >> an embedded machine and rarely are there people in front of embedded >> computers these days. > > I did run into a practical problem. Hardware watchdogs on embedded > systems can have short timers on the order of seconds. If the system > is locked up for a few seconds with only a single core available, the > watchdog may not be pet in a timely fashion. If this happens, the > hardware watchdog will fire and reset the system. > > This really only becomes a problem when you are working with a single > core, a decently sized initrd, and have a constrained hardware > watchdog. That would do it. My foggy memory says this was not included back in the days where cond_resched was spelled "if (need_resched) schedule();" There were concerns with spreading that too thin. cond_resched in this path seems as reasonable as anything. Eric