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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DB29CC433DB for ; Thu, 25 Mar 2021 12:12:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B14961A07 for ; Thu, 25 Mar 2021 12:12:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230175AbhCYMLw (ORCPT ); Thu, 25 Mar 2021 08:11:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49208 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229533AbhCYMLq (ORCPT ); Thu, 25 Mar 2021 08:11:46 -0400 Received: from hr2.samba.org (hr2.samba.org [IPv6:2a01:4f8:192:486::2:0]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8A224C06174A; Thu, 25 Mar 2021 05:11:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=samba.org; s=42; h=Date:Message-ID:From:Cc:To; bh=miwPIcGRmxLognFQqT73uzsqflhmzM1L7+w2rU8vpmM=; b=0zO0h1f70agryRb7uyRn/iCH5S W7b5b1W1pqfnbUHSIeHQAG468ootZEDLihJFyseJAxE4CPkwGFtedVi26Pcedayo0SVaTAxfkI+oK ENROBq/YJ31yjgKoeOMnarCMxdNOrYWRIRVQMHfwjxGTLjl3sorunH+BQl2SFoncF+JTvvTP8o1tJ j1oiMkKHkMyUV4RVjv+eCTGWox2eJxrhEF7D7amj/3fBKIA6do+CSJpmtsXjdKTklZ7z1vqzYdZH4 QaumKP9rvOqH9/UwPP5XjQXoq+AaJXPwjJSzoqgs+TM1rMyKlVZ2mOBo9s4ipES+uvfNy+1Jl3wNx ElY3iN4OsnlfCefug4wMrkrf65uTSSpPStDlGkAkSybeDmOa/jH6Too3gH4lDpcouf97kXAXH2KE2 me02RrMSTsYolwGRfGIbVOUvxaZvxnrn42NOYvo/dUn/kSSKaVPtyjBuFI7TIMtnzv65ErmCVvMeg hUj2X5e5uu9N3rbwY1xpAIvr; Received: from [127.0.0.2] (localhost [127.0.0.1]) by hr2.samba.org with esmtpsa (TLS1.3:ECDHE_RSA_CHACHA20_POLY1305:256) (Exim) id 1lPOpz-0007nn-AF; Thu, 25 Mar 2021 12:11:43 +0000 To: "Eric W. Biederman" Cc: Sasha Levin , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Jens Axboe , io-uring , Linus Torvalds References: <20210325112459.1926846-1-sashal@kernel.org> <20210325112459.1926846-43-sashal@kernel.org> From: Stefan Metzmacher Subject: Re: [PATCH AUTOSEL 5.11 43/44] signal: don't allow STOP on PF_IO_WORKER threads Message-ID: <41589c56-9219-3ec2-55b3-3f010752ac7b@samba.org> Date: Thu, 25 Mar 2021 13:11:41 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 25.03.21 um 13:04 schrieb Eric W. Biederman: > Stefan Metzmacher writes: > >> Am 25.03.21 um 12:24 schrieb Sasha Levin: >>> From: "Eric W. Biederman" >>> >>> [ Upstream commit 4db4b1a0d1779dc159f7b87feb97030ec0b12597 ] >>> >>> Just like we don't allow normal signals to IO threads, don't deliver a >>> STOP to a task that has PF_IO_WORKER set. The IO threads don't take >>> signals in general, and have no means of flushing out a stop either. >>> >>> Longer term, we may want to look into allowing stop of these threads, >>> as it relates to eg process freezing. For now, this prevents a spin >>> issue if a SIGSTOP is delivered to the parent task. >>> >>> Reported-by: Stefan Metzmacher >>> Signed-off-by: Jens Axboe >>> Signed-off-by: "Eric W. Biederman" >>> Signed-off-by: Sasha Levin >>> --- >>> kernel/signal.c | 3 ++- >>> 1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/kernel/signal.c b/kernel/signal.c >>> index 55526b941011..00a3840f6037 100644 >>> --- a/kernel/signal.c >>> +++ b/kernel/signal.c >>> @@ -288,7 +288,8 @@ bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask) >>> JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING)); >>> BUG_ON((mask & JOBCTL_TRAPPING) && !(mask & JOBCTL_PENDING_MASK)); >>> >>> - if (unlikely(fatal_signal_pending(task) || (task->flags & PF_EXITING))) >>> + if (unlikely(fatal_signal_pending(task) || >>> + (task->flags & (PF_EXITING | PF_IO_WORKER)))) >>> return false; >>> >>> if (mask & JOBCTL_STOP_SIGMASK) >>> >> >> Again, why is this proposed for 5.11 and 5.10 already? > > Has the bit about the io worker kthreads been backported? > If so this isn't horrible. If not this is nonsense. I don't know, I hope not... But I just tested v5.12-rc4 and attaching to an application with iothreads with gdb is still not possible, it still loops forever trying to attach to the iothreads. And I tested 'kill -9 $pidofiothread', and it feezed the whole machine... So there's still work to do in order to get 5.12 stable. I'm short on time currently, but I hope to send more details soon. metze