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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 568B7C77B7E for ; Sun, 28 May 2023 01:42:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229476AbjE1Bll (ORCPT ); Sat, 27 May 2023 21:41:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33328 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229437AbjE1Blj (ORCPT ); Sat, 27 May 2023 21:41:39 -0400 Received: from out03.mta.xmission.com (out03.mta.xmission.com [166.70.13.233]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1CA12D8 for ; Sat, 27 May 2023 18:41:39 -0700 (PDT) Received: from in02.mta.xmission.com ([166.70.13.52]:38252) by out03.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1q35Pd-004hje-8d; Sat, 27 May 2023 19:41:37 -0600 Received: from ip68-110-29-46.om.om.cox.net ([68.110.29.46]:55318 helo=email.froward.int.ebiederm.org.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1q35Pb-003vjS-Tg; Sat, 27 May 2023 19:41:36 -0600 From: "Eric W. Biederman" To: Mike Christie Cc: Oleg Nesterov , linux@leemhuis.info, nicolas.dichtel@6wind.com, axboe@kernel.dk, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, mst@redhat.com, sgarzare@redhat.com, jasowang@redhat.com, stefanha@redhat.com, brauner@kernel.org References: <20230522025124.5863-1-michael.christie@oracle.com> <20230522025124.5863-4-michael.christie@oracle.com> <20230522123029.GA22159@redhat.com> <20230522174757.GC22159@redhat.com> <20230523121506.GA6562@redhat.com> Date: Sat, 27 May 2023 20:41:29 -0500 In-Reply-To: (Mike Christie's message of "Thu, 25 May 2023 11:15:59 -0500") Message-ID: <87a5xpkzau.fsf@email.froward.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1q35Pb-003vjS-Tg;;;mid=<87a5xpkzau.fsf@email.froward.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.110.29.46;;;frm=ebiederm@xmission.com;;;spf=pass X-XM-AID: U2FsdGVkX1+V2Qg3ULEu3+aeUbHP6A32iBYl7ldKMoo= X-SA-Exim-Connect-IP: 68.110.29.46 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 3/3] fork, vhost: Use CLONE_THREAD to fix freezer/ps regression X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Mike Christie writes: > On 5/23/23 7:15 AM, Oleg Nesterov wrote: >> >> Now the main question. Whatever we do, SIGKILL/SIGSTOP/etc can come right >> before we call work->fn(). Is it "safe" to run this callback with >> signal_pending() or fatal_signal_pending() ? > > The questions before this one I'll leave for the core vhost devs since > they know best. Let me ask a clarifying question: Is it only the call to schedule() in vhost_worker that you are worried about not sleeping if signal_pending() or fatal_signal_pending()? Is there concern that the worker functions aka "work->fn()" will also have killable or interruptible sleeps that also will misbehave. We can handle schedule() in vhost_worker without problem. If a worker function has interruptible or killable sleeps that will turn into busy waits or worse not sleeping long enough that seems like a problem. There is no way to guarantee that the outer loop of vhost_worker will protect the worker functions from signal_pending() or fatal_signal_pending() becoming true. Eric