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[23.128.96.33]) by mx.google.com with ESMTPS id d4-20020a056a0010c400b00690fec2f3b6si3291667pfu.193.2023.10.19.04.55.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Oct 2023 04:55:55 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.33 as permitted sender) client-ip=23.128.96.33; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=k20201202 header.b=kf6TULOc; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.33 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by lipwig.vger.email (Postfix) with ESMTP id 2BD5C8043ECB; Thu, 19 Oct 2023 04:55:24 -0700 (PDT) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.10 at lipwig.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235310AbjJSLzH (ORCPT + 25 others); Thu, 19 Oct 2023 07:55:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33226 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235234AbjJSLzD (ORCPT ); Thu, 19 Oct 2023 07:55:03 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5A295BE; Thu, 19 Oct 2023 04:55:02 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9756C433CA; Thu, 19 Oct 2023 11:54:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697716502; bh=sSbMY5CCWBmj3HxnZsWM2SzuTJFQ7pmsTLrLgETzDzc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kf6TULOcwoQ0k/urPmEbr8nA8gx7X3lqPGmstxbvYn5iU5ujZYgb7H9MoGR3aZynj pBURPPNLMy0as1zjtoRzybBs4P55OuBhVf69lgs8PEXMWC9a1mPYjkURxsWW26mGDr aQUuIyzaPB2qPXjhTfjgAG/2NE71zTlCrDlrHAIuFK5rzUADAfFL6wXQp36ZHYAfpw 7F0KUMeQ2wzVscwt8DSPnRdweG0vnIMLN9AUY52N6YsliJUHVuiPImkRSa+Am/BzOF W82uvz9a1b0iKfh/7WCqJC/s1UAYjM1JDhAxt7JzkPbQww6QLQTRpEg9P9LEkGmNu/ Vyskb1/quY7QA== From: Frederic Weisbecker To: LKML Cc: "Paul E. McKenney" , Boqun Feng , Joel Fernandes , Josh Triplett , Mathieu Desnoyers , Neeraj Upadhyay , Steven Rostedt , Uladzislau Rezki , rcu , Frederic Weisbecker Subject: [PATCH 1/3] refscale: Fix misplaced data re-read Date: Thu, 19 Oct 2023 13:54:50 +0200 Message-Id: <20231019115452.1215974-2-frederic@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231019115452.1215974-1-frederic@kernel.org> References: <20231019115452.1215974-1-frederic@kernel.org> MIME-Version: 1.0 X-Spam-Status: No, score=-1.2 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lipwig.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (lipwig.vger.email [0.0.0.0]); Thu, 19 Oct 2023 04:55:24 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1780184835168936316 X-GMAIL-MSGID: 1780184835168936316 From: "Paul E. McKenney" This commit fixes a misplaced data re-read in the typesafe code. The reason that this was not noticed is that this is a performance test with no writers, so a mismatch could not occur. Signed-off-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker --- kernel/rcu/refscale.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c index 91a0fd0d4d9a..750a63e99539 100644 --- a/kernel/rcu/refscale.c +++ b/kernel/rcu/refscale.c @@ -655,12 +655,12 @@ static void typesafe_delay_section(const int nloops, const int udl, const int nd goto retry; } un_delay(udl, ndl); + b = READ_ONCE(rtsp->a); // Remember, seqlock read-side release can fail. if (!rts_release(rtsp, start)) { rcu_read_unlock(); goto retry; } - b = READ_ONCE(rtsp->a); WARN_ONCE(a != b, "Re-read of ->a changed from %u to %u.\n", a, b); b = rtsp->b; rcu_read_unlock();