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=-10.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 E20C8C433FE for ; Tue, 8 Dec 2020 13:11:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ADB0C23AA7 for ; Tue, 8 Dec 2020 13:11:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726584AbgLHNLe (ORCPT ); Tue, 8 Dec 2020 08:11:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53664 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726483AbgLHNLd (ORCPT ); Tue, 8 Dec 2020 08:11:33 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92BB1C061749 for ; Tue, 8 Dec 2020 05:10:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; 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=nxtHzv3G9CEsPKPHZfP9UfNvs7B1c+41sN5DQUZcSLw=; b=sM+C6cWEp/UxfITu1s664UuzM/ KtCXekYwrglfLhLy6D/RD6L44Acm7LKZvypGQS3AWpwsDNkzWHKiQdtq09R62M8ETESngQfpRvBTl M9f10LNE/OPkNJ8nZjN3D/oe7bKqi4ftmXvVz2gvLqrX8LWT2ZexyfcQZSLIsHzjajjH2HNKW+R/i cGeg7cFQDXW4/ZA53vh/lll4g3Y467lCNRbPUtVJBwL2oAUCHRsf/0E11go14GF1sjSwSBUF83LTJ RUb6EsqVHqnB1ado+dxtvcBCJz/EgmScMOyx9ng0DXJhTYsAAFWs8geJI4Smst8FsrEMySuz7hmvf n1WzFCyA==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kmclV-0005nK-Ds; Tue, 08 Dec 2020 13:10:49 +0000 Date: Tue, 8 Dec 2020 13:10:49 +0000 From: Christoph Hellwig To: Sebastian Andrzej Siewior Cc: linux-block@vger.kernel.org, Jens Axboe , Thomas Gleixner , Peter Zijlstra , Daniel Wagner , Mike Galbraith , Christoph Hellwig , Sagi Grimberg Subject: Re: [PATCH 1/3] blk-mq: Don't complete on a remote CPU in force threaded mode Message-ID: <20201208131049.GA22219@infradead.org> References: <20201204191356.2516405-1-bigeasy@linutronix.de> <20201204191356.2516405-2-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201204191356.2516405-2-bigeasy@linutronix.de> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Fri, Dec 04, 2020 at 08:13:54PM +0100, Sebastian Andrzej Siewior wrote: > With force threaded interrupts enabled, raising softirq from an SMP > function call will always result in waking the ksoftirqd thread. This is > not optimal given that the thread runs at SCHED_OTHER priority. > > Completing the request in hard IRQ-context on PREEMPT_RT (which enforces > the force threaded mode) is bad because the completion handler may > acquire sleeping locks which violate the locking context. > > Disable request completing on a remote CPU in force threaded mode. > > Signed-off-by: Sebastian Andrzej Siewior Looks good, Reviewed-by: Christoph Hellwig