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 099E5C77B7A for ; Tue, 16 May 2023 18:39:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229908AbjEPSjH (ORCPT ); Tue, 16 May 2023 14:39:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229498AbjEPSjF (ORCPT ); Tue, 16 May 2023 14:39:05 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC98610F9 for ; Tue, 16 May 2023 11:38:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1684262300; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=bR7XFUDwDwS2QCuwLOFs/PBnLvy7FY7D7eHZBo5Cn1w=; b=GWX6e1QLXUmS8XRGslSSnWAozRYrkSuB+E806Q3nEHdaTeQ/M1WLKNzaUTvW1m3k45/QXo 1WqqMHzIgjnUQ4DdtpNYSD0gKcD8EG1mlEXuR/vYsVVvhgaF4VrWtkz0FB9eYwu23SAwnK h/C7JJg+xK6NRm/IabqXE+oloSJaEcg= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-288-Qs50wazRPeS9HugWOpEC4A-1; Tue, 16 May 2023 14:38:16 -0400 X-MC-Unique: Qs50wazRPeS9HugWOpEC4A-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id E5D5D2802537; Tue, 16 May 2023 18:38:15 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.226.147]) by smtp.corp.redhat.com (Postfix) with SMTP id F1DD22166B31; Tue, 16 May 2023 18:38:11 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 16 May 2023 20:38:02 +0200 (CEST) Date: Tue, 16 May 2023 20:37:57 +0200 From: Oleg Nesterov To: "Eric W. Biederman" Cc: Linus Torvalds , Mike Christie , Christian Brauner , Thorsten Leemhuis , nicolas.dichtel@6wind.com, Linux kernel regressions list , hch@infradead.org, stefanha@redhat.com, jasowang@redhat.com, mst@redhat.com, sgarzare@redhat.com, virtualization@lists.linux-foundation.org, konrad.wilk@oracle.com, linux-kernel@vger.kernel.org, Jens Axboe Subject: Re: [PATCH v11 8/8] vhost: use vhost_tasks for worker threads Message-ID: <20230516183757.GA1286@redhat.com> References: <78c5e150-26cf-7724-74ee-4a0b16b944b1@oracle.com> <48842e92-835e-bc3f-7118-48b8f415f532@leemhuis.info> <20230515-vollrausch-liebgeworden-2765f3ca3540@brauner> <122b597e-a5fa-daf7-27bb-6f04fa98d496@oracle.com> <87cz30s20y.fsf@email.froward.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87cz30s20y.fsf@email.froward.int.ebiederm.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/16, Eric W. Biederman wrote: > > A kernel thread can block SIGKILL and that is supported. > > For a thread that is part of a process you can't block SIGKILL when the > task is part of a user mode process. Or SIGSTOP. Another thread can call do_signal_stop()->signal_wake_up/etc. > There is this bit in complete_signal when SIGKILL is delivered to any > thread in the process. > > t = p; > do { > task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK); > sigaddset(&t->pending.signal, SIGKILL); > signal_wake_up(t, 1); > } while_each_thread(p, t); That is why the latest version adds try_set_pending_sigkill(). No, no, it is not that I think this is a good idea. > For clarity that sigaddset(&t->pending.signal, SIGKILL); Really isn't > setting SIGKILL pending, Hmm. it does? Nevermind. > The important part of that code is that SIGNAL_GROUP_EXIT gets set. > That indicates the entire process is being torn down. Yes. and the same is true for io-thread even if it calls get_signal() and dequeues SIGKILL and clears TIF_SIGPENDING. > but in that case the vhost logic needs to act like a process, just > like io_uring does. confused... create_io_thread() creates a sub-thread too? Although I never understood this logic. I can't even understand the usage of lower_32_bits() in create_io_thread(). Oleg.