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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 234E9C433E7 for ; Sat, 17 Oct 2020 15:31:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D16B82072C for ; Sat, 17 Oct 2020 15:31:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="bO29nU6v"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="PlIGX9nM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2438524AbgJQPbp (ORCPT ); Sat, 17 Oct 2020 11:31:45 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:50418 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2438516AbgJQPbp (ORCPT ); Sat, 17 Oct 2020 11:31:45 -0400 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1602948703; 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=h+yVwEx6UlSb28MYyb4hCQ5aam028HimOBjq54tjfPM=; b=bO29nU6vbkENaUbtkZDhzX6JQpr34nUvwFGH82umQbNaFc3Qn/sLCakWiyTMk2PyiuqR5c GkPt7VBGxbgvX1/+XJCwdFJt6jAKpqsQma0U5PNagYBmGgUotLFaAZMHYhOcOA9dwU4s9O 4mxP2fJNhynuh0Kyq12taF0yO5iTODKGzGZCJooxa4AqjeN0BdeYt4+W5eAuXn6/ISnX3B 1hAz/2FbSXmAuIVYgWhupFO7d9IexuYd18HPG7v45OZOIf1w/cjlwMeGlGpHPv5J5srEly L/xl9yoFWHdtvIqtnVfeH5T+963KccxFXpLTH60PLvgoCD6HpcGn9xuvYfloyQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1602948703; 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=h+yVwEx6UlSb28MYyb4hCQ5aam028HimOBjq54tjfPM=; b=PlIGX9nMZGMlbtaW6uJ9Dprx+ikXwso11iDryJgujIlC7s6sbggSa/nrRrFcYBEUVIR/8a hxyIfc4juU6qVpBQ== To: Jens Axboe Cc: "linux-kernel\@vger.kernel.org" Subject: Re: [PATCH] task_work: cleanup notification modes In-Reply-To: <7e32aa44-35ff-3a48-87d0-8e7df586db1d@kernel.dk> References: <93292d5b-9124-d252-c81f-1f2cfbd60e7b@kernel.dk> <87tuutalre.fsf@nanos.tec.linutronix.de> <87zh4lix8l.fsf@nanos.tec.linutronix.de> <2ebe7e45-b4e5-1a6b-d3ee-4a790817a119@kernel.dk> <87wnzpivvx.fsf@nanos.tec.linutronix.de> <7e32aa44-35ff-3a48-87d0-8e7df586db1d@kernel.dk> Date: Sat, 17 Oct 2020 17:31:42 +0200 Message-ID: <87tuusj2ch.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 16 2020 at 17:43, Jens Axboe wrote: > On 10/16/20 5:38 PM, Thomas Gleixner wrote: > If you know the task isn't exiting, then yeah you can ignore it. But > seems a bit dicey... Indeed. >> fs/io_uring.c- if (unlikely(ret)) { >> fs/io_uring.c- struct task_struct *tsk; >> fs/io_uring.c- >> fs/io_uring.c- init_task_work(&req->task_work, io_req_task_cancel); >> fs/io_uring.c- tsk = io_wq_get_task(req->ctx->io_wq); >> fs/io_uring.c: task_work_add(tsk, &req->task_work, 0); >> fs/io_uring.c- wake_up_process(tsk); >> >> yet more magic wakeup. > > It's not magic, but probably needs a comment... If we fail, that task is > exiting. But we know we have our io-wq threads, so we use that as a > fallback. Not really expected in the fast path. I somehow misread it. So ignore me. Thanks, tglx