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=-8.7 required=3.0 tests=BAYES_00, 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 E06A4C433E6 for ; Wed, 27 Jan 2021 11:26:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 93D632078E for ; Wed, 27 Jan 2021 11:26:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236512AbhA0L0P (ORCPT ); Wed, 27 Jan 2021 06:26:15 -0500 Received: from mx2.suse.de ([195.135.220.15]:42112 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236573AbhA0LYN (ORCPT ); Wed, 27 Jan 2021 06:24:13 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 30C22B7CB; Wed, 27 Jan 2021 11:23:32 +0000 (UTC) Date: Wed, 27 Jan 2021 12:23:31 +0100 From: Daniel Wagner To: Sebastian Andrzej Siewior Cc: Christoph Hellwig , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Jens Axboe , Thomas Gleixner , Peter Zijlstra , Ingo Molnar Subject: Re: [PATCH 3/3 v2] blk-mq: Use llist_head for blk_cpu_done Message-ID: <20210127112331.bew6os5jfyvjzhwj@beryllium.lan> References: <20210123201027.3262800-1-bigeasy@linutronix.de> <20210123201027.3262800-4-bigeasy@linutronix.de> <20210125083012.GD942655@infradead.org> <20210125083204.ahddujk5m6njwbju@linutronix.de> <20210125083903.GB945284@infradead.org> <20210125095412.qxknd2vbsmgtrhqb@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210125095412.qxknd2vbsmgtrhqb@linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Jan 25, 2021 at 10:54:12AM +0100, Sebastian Andrzej Siewior wrote: > With llist_head it is possible to avoid the locking (the irq-off region) > when items are added. This makes it possible to add items on a remote > CPU without additional locking. > llist_add() returns true if the list was previously empty. This can be > used to invoke the SMP function call / raise sofirq only if the first > item was added (otherwise it is already pending). > This simplifies the code a little and reduces the IRQ-off regions. > > blk_mq_raise_softirq() needs a preempt-disable section to ensure the > request is enqueued on the same CPU as the softirq is raised. > Some callers (USB-storage) invoke this path in preemptible context. > > Signed-off-by: Sebastian Andrzej Siewior I did a quick test run with the whole series. Looks good. Reviewed-by: Daniel Wagner