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=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 4C2BBC2BB55 for ; Tue, 7 Apr 2020 11:54:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 16E6B206C0 for ; Tue, 7 Apr 2020 11:54:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Szv5ioe5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728474AbgDGLy3 (ORCPT ); Tue, 7 Apr 2020 07:54:29 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:20306 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726562AbgDGLy3 (ORCPT ); Tue, 7 Apr 2020 07:54:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1586260468; 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=et3zCqB0E1hcw15aKztJyuVcB59NERyG2SoCCOuTaRg=; b=Szv5ioe5Y6ZMfGElxTZnJCy87XUVGItVaYbOmTKjWzAzfjROmiPJIx/UutONe4nBENEKLZ WBbC+J58O/IFtTd3QIV5QpbsT6pJ/MzekVWiXQ2lNyv4IDeCVyhEVHiLk2sMTUfyaftaff MDM1BwB9AFNa3BHNRQiEacwPXhTgG+I= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-440-C0Ps29etOIKitNIMv1KjHw-1; Tue, 07 Apr 2020 07:54:27 -0400 X-MC-Unique: C0Ps29etOIKitNIMv1KjHw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0082413F7; Tue, 7 Apr 2020 11:54:26 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.196.88]) by smtp.corp.redhat.com (Postfix) with SMTP id 9D7E69D37A; Tue, 7 Apr 2020 11:54:24 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 7 Apr 2020 13:54:25 +0200 (CEST) Date: Tue, 7 Apr 2020 13:54:23 +0200 From: Oleg Nesterov To: Jens Axboe Cc: io-uring@vger.kernel.org, peterz@infradead.org Subject: Re: [PATCH 2/4] task_work: don't run task_work if task_work_exited is queued Message-ID: <20200407115423.GC4506@redhat.com> References: <20200406194853.9896-1-axboe@kernel.dk> <20200406194853.9896-3-axboe@kernel.dk> <20200407113927.GB4506@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200407113927.GB4506@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 04/07, Oleg Nesterov wrote: > > On 04/06, Jens Axboe wrote: > > > > +extern struct callback_head task_work_exited; > > + > > static inline void > > init_task_work(struct callback_head *twork, task_work_func_t func) > > { > > @@ -19,7 +21,7 @@ void __task_work_run(void); > > > > static inline bool task_work_pending(void) > > { > > - return current->task_works; > > + return current->task_works && current->task_works != &task_work_exited; > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > Well, this penalizes all the current users, they can't hit work_exited. > > IIUC, this is needed for the next change which adds task_work_run() into > io_ring_ctx_wait_and_kill(), right? > > could you explain how the exiting can call io_ring_ctx_wait_and_kill() > after it passed exit_task_work() ? Note also that currently we assume that task_work_run() must not be called by the exiting process (except exit_task_work). If io_ring adds the precedent we need change the PF_EXITING logic in task_work_run(). Oleg.