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 A70E3C77B73 for ; Mon, 22 May 2023 12:35:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233289AbjEVMfs (ORCPT ); Mon, 22 May 2023 08:35:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37310 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234413AbjEVMf0 (ORCPT ); Mon, 22 May 2023 08:35:26 -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 3F96FAC for ; Mon, 22 May 2023 05:33:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1684758655; 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=XLKVwpsofT3fO0KfbhEhMNwUy6j+Hh9Xz3u/5JzJISE=; b=VrQZEWcwHaXvKGFIvkldpISREdu5SG3OLca38Ti4SRnijzGBg1peBWC2B+JScu3kW4Z9gZ r3H1nLuHPwvWwRIwzRvjiDWm+U3XTKimhR0n1BGWD+f7F+s4Y/lb/qqeGe6ldRgxyI6Dp1 6tPBlBKolsf8slvyaOPQMaFGvV3Etvk= 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-612-y0yXY8u3NEe6cP21B_llfw-1; Mon, 22 May 2023 08:30:50 -0400 X-MC-Unique: y0yXY8u3NEe6cP21B_llfw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D051B185A78F; Mon, 22 May 2023 12:30:49 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.202]) by smtp.corp.redhat.com (Postfix) with SMTP id BD2D7407DEC3; Mon, 22 May 2023 12:30:46 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 22 May 2023 14:30:33 +0200 (CEST) Date: Mon, 22 May 2023 14:30:29 +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: <20230522123029.GA22159@redhat.com> References: <20230522025124.5863-1-michael.christie@oracle.com> <20230522025124.5863-4-michael.christie@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230522025124.5863-4-michael.christie@oracle.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Confused, please help... On 05/21, Mike Christie wrote: > > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -338,6 +338,7 @@ static int vhost_worker(void *data) > struct vhost_worker *worker = data; > struct vhost_work *work, *work_next; > struct llist_node *node; > + bool dead = false; > > for (;;) { > /* mb paired w/ kthread_stop */ > @@ -349,8 +350,22 @@ static int vhost_worker(void *data) > } > > node = llist_del_all(&worker->work_list); > - if (!node) > + if (!node) { > schedule(); > + /* > + * 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 ? > + if (!dead && signal_pending(current)) { > + struct ksignal ksig; > + > + dead = get_signal(&ksig); > + if (dead) > + clear_thread_flag(TIF_SIGPENDING); If you do clear_thread_flag(TIF_SIGPENDING), then why do we need 1/3 ? 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? Oleg.