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[2620:137:e000::1:20]) by mx.google.com with ESMTP id s2-20020a2e9c02000000b0024eef7ce4e9si6923559lji.264.2022.04.29.07.28.44; Fri, 29 Apr 2022 07:29:12 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=desiato.20200630 header.b=oywOchgo; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345020AbiD1JMU (ORCPT + 99 others); Thu, 28 Apr 2022 05:12:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50632 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344972AbiD1JMB (ORCPT ); Thu, 28 Apr 2022 05:12:01 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 453B753E19 for ; Thu, 28 Apr 2022 02:08:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Nr3EW08QcY2FGP18WwgBhQtNIE2zBp0aUeKcrHOynmM=; b=oywOchgoz1yVCmHP152iFQ65z9 eTcv5VKYmC1Zf1NaA6nati1neDOaJSHiHEdvfnkoOtg8ilR7Shgv/XkhQDXU7F6BOO3CZiVT5MtFt YgkOQLEfnhDucY6Oi0/Z5gv91qMtuk9MO/quSySVQJrqgjpAu+oyLPTNLUd/SoMqCVo6Qln/jdoJO pVymNFE5nlVMiX3+8qPM37AK1mn1Nq+nWlCk3eBCWemwZAMH7rb80Oziwra2xbibrU2dPYvNQM1Uf 8Umd3NytBiKm2mhO20dzbsM+hnWtzXFHiyPSx2NmUiZb5plj6sTcdASL/MB7a2PeNGSTDv+tVVg+E hniOlErg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nk08c-009JCw-Pp; Thu, 28 Apr 2022 09:08:39 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 9FC43981710; Thu, 28 Apr 2022 11:08:36 +0200 (CEST) Date: Thu, 28 Apr 2022 11:08:36 +0200 From: Peter Zijlstra To: Jens Axboe Cc: LKML , tglx@linutronix.de Subject: Re: [PATCH] task_work: allow TWA_SIGNAL without a rescheduling IPI Message-ID: <20220428090836.GQ2731@worktop.programming.kicks-ass.net> References: <543452ca-f82e-4f00-cd51-88bb9723a975@kernel.dk> <33a6de15-f487-b12b-8ffe-af978ebb03c3@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <33a6de15-f487-b12b-8ffe-af978ebb03c3@kernel.dk> X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 25, 2022 at 07:52:31PM -0600, Jens Axboe wrote: > On 4/22/22 8:34 AM, Jens Axboe wrote: > > Some use cases don't always need an IPI when sending a TWA_SIGNAL > > notification. Add TWA_SIGNAL_NO_IPI, which is just like TWA_SIGNAL, > > except it doesn't send an IPI to the target task. It merely sets > > TIF_NOTIFY_SIGNAL and wakes up the task. Could you perphaps elaborate on those use-cases? How do they guarantee the task_work is ran before userspace?