From patchwork Wed Apr 24 21:54:17 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Stefan_B=C3=BChler?= X-Patchwork-Id: 10915789 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 06D961575 for ; Wed, 24 Apr 2019 21:54:27 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EBEDB28B9B for ; Wed, 24 Apr 2019 21:54:26 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id DFE9728B9C; Wed, 24 Apr 2019 21:54:26 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,DKIM_ADSP_ALL, DKIM_INVALID,DKIM_SIGNED,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 14F8328BA0 for ; Wed, 24 Apr 2019 21:54:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731789AbfDXVyZ (ORCPT ); Wed, 24 Apr 2019 17:54:25 -0400 Received: from mail.stbuehler.de ([5.9.32.208]:41006 "EHLO mail.stbuehler.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728103AbfDXVyZ (ORCPT ); Wed, 24 Apr 2019 17:54:25 -0400 Received: from chromobil.fritz.box (unknown [IPv6:2a02:8070:a29c:5000:823f:5dff:fe0f:b5b6]) by mail.stbuehler.de (Postfix) with ESMTPSA id F28ACC0305A; Wed, 24 Apr 2019 21:54:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=stbuehler.de; s=stbuehler1; t=1556142863; bh=0RSvUxsIo8Ibx3xQwGcriYo415sDbopj8zmEKzbZIuI=; h=From:To:Subject:Date:In-Reply-To:References:From; b=xPwO9BM7hjfYr14fD+FwgCVfHuoR9lt1JaprgMYcW/YIZsjJysOBh/L/D/2LpfN0q OuV21fIXd2eiO0ewdL41d27HmLswhB+Sf1zQFSeXpCRz2zHNELhsg9+TZc10X7T1Yt 3NMyvqtqrYRUpRa5P/Pigs059hIkrdGBOfyofU7Y= From: =?utf-8?q?Stefan_B=C3=BChler?= To: Jens Axboe , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH barrier cleanup v1 2/7] io_uring: remove unnecessary barrier before wq_has_sleeper Date: Wed, 24 Apr 2019 23:54:17 +0200 Message-Id: <20190424215422.7404-2-source@stbuehler.de> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190424215422.7404-1-source@stbuehler.de> References: <54496e17-97de-9f9a-9972-c448226bb768@stbuehler.de> <20190424215422.7404-1-source@stbuehler.de> MIME-Version: 1.0 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP wq_has_sleeper has a full barrier internally. The smp_rmb barrier in io_uring_poll synchronizes with it. Signed-off-by: Stefan Bühler --- fs/io_uring.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 7025e9830abe..1f4419f38ef1 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -418,12 +418,6 @@ static void io_commit_cqring(struct io_ring_ctx *ctx) /* order cqe stores with ring update */ smp_store_release(&ring->r.tail, ctx->cached_cq_tail); - /* - * Write sider barrier of tail update, app has read side. See - * comment at the top of this file. - */ - smp_wmb(); - if (wq_has_sleeper(&ctx->cq_wait)) { wake_up_interruptible(&ctx->cq_wait); kill_fasync(&ctx->cq_fasync, SIGIO, POLL_IN); @@ -2674,7 +2668,9 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait) __poll_t mask = 0; poll_wait(file, &ctx->cq_wait, wait); - /* See comment at the top of this file */ + /* synchronizes with barrier from wq_has_sleeper call in + * io_commit_cqring + */ smp_rmb(); if (READ_ONCE(ctx->sq_ring->r.tail) - ctx->cached_sq_head != ctx->sq_ring->ring_entries)