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 A5021C77B73 for ; Mon, 22 May 2023 17:49:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232973AbjEVRtN (ORCPT ); Mon, 22 May 2023 13:49:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51428 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232901AbjEVRtK (ORCPT ); Mon, 22 May 2023 13:49:10 -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 9B9DEFF for ; Mon, 22 May 2023 10:48:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1684777702; 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=b7LSkGuXeXqte2Z5Adf2PWVtK/h6XyI9Wqw3/+z8Mgw=; b=Fe9S92bw4lb0phNnSvA29psaM8TsE1afHolDYUDexdsjgcnLvhjTHnwmAtlDeeQlsCU/hc qQYuZrXvcruviIncJssXll8iUb9ftO176IX44DT/zV9MvtK1M+W5+4k5rkhsdslPG3BzFJ BmTGKv8pfCUQweiyjN0myZTxsQqUuc4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-150-Z9dhIrpdOzKq_gulj_8cBw-1; Mon, 22 May 2023 13:48:19 -0400 X-MC-Unique: Z9dhIrpdOzKq_gulj_8cBw-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 20E2B811E94; Mon, 22 May 2023 17:48:18 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.202]) by smtp.corp.redhat.com (Postfix) with SMTP id 42E2A2166B25; Mon, 22 May 2023 17:48:15 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 22 May 2023 19:48:01 +0200 (CEST) Date: Mon, 22 May 2023 19:47:58 +0200 From: Oleg Nesterov To: Mike Christie Cc: linux@leemhuis.info, nicolas.dichtel@6wind.com, axboe@kernel.dk, ebiederm@xmission.com, 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 Subject: Re: [PATCH 3/3] fork, vhost: Use CLONE_THREAD to fix freezer/ps regression Message-ID: <20230522174757.GC22159@redhat.com> References: <20230522025124.5863-1-michael.christie@oracle.com> <20230522025124.5863-4-michael.christie@oracle.com> <20230522123029.GA22159@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 05/22, Mike Christie wrote: > > On 5/22/23 7:30 AM, Oleg Nesterov wrote: > >> + /* > >> + * When we get a SIGKILL our release function will > >> + * be called. That will stop new IOs from being queued > >> + * and check for outstanding cmd responses. It will then > >> + * call vhost_task_stop to tell us to return and exit. > >> + */ > > > > But who will call the release function / vhost_task_stop() and when this > > will happen after this thread gets SIGKILL ? > > When we get a SIGKILL, the thread that owns the device/vhost_task will > also exit since it's the same thread group and it does: > > do_exit -> exit_files -> put_files_struct -> close_files -> fput Ah. thanks. I confused CLONE_FS in vhost_task_create() with CLONE_FILES. > > Also. Suppose that vhost_worker() dequeues SIGKILL and clears TIF_SIGPENDING. > > > > SIGSTOP, PTRACE_INTERRUPT, freezer can come and set TIF_SIGPENDING again. > > In this case the main for (;;) loop will spin without sleeping until > > vhost_task_should_stop() becomes true? > > I see. So I either have to be able to call get_signal after SIGKILL or > at this time work like a kthread and ignore signals like a > > if (dead && signal_pending()) > flush_signals() > ? Right now I think that "int dead" should die, and you should simply do get_signal() + clear(SIGPENDING) if signal_pending() == T , but let me think tomorrow. Oleg.