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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 09886C35242 for ; Sat, 15 Feb 2020 00:29:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CCD4820848 for ; Sat, 15 Feb 2020 00:29:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581726587; bh=AM7BWBBRULXhHF5jNwhG2VL7NvzrkRoAiUsPNZ5Bbbo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Lfbz0qnjA7gd1cKoZiy4JXl7celrFGbY00wZh/tIBQE/4Ipc50jXYvLR2qkV5fgcu OwShexJZBUNSjt6sYTLuhN27cVXKR4lJ69236AHI2HLG/7jymE3W10Bir59ms85FJD vskkEcFcXodXJnz0ucdOUgrMDskG2FbFM9IH6BRo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727529AbgBOA3r (ORCPT ); Fri, 14 Feb 2020 19:29:47 -0500 Received: from mail.kernel.org ([198.145.29.99]:45446 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727567AbgBOA3r (ORCPT ); Fri, 14 Feb 2020 19:29:47 -0500 Received: from paulmck-ThinkPad-P72.c.hoisthospitality.com (unknown [62.84.152.189]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 97EF42187F; Sat, 15 Feb 2020 00:29:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581726586; bh=AM7BWBBRULXhHF5jNwhG2VL7NvzrkRoAiUsPNZ5Bbbo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=foExSxWZabAGXAuD2q9Vizf0A2nLrwgCLQC8AE026UtTPhXLritza7vMrianNw9ta RShVuyeZ0ACTiZT5++qIOB4FlYvCl1Cfd3eAu6as6GoNX2D4lz1pOuoIMOP0EHBswf DtdMSHSrMIbbbqlVOz5ueVvd9iGUrhPZhECWO1Jo= From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 3/4] srcu: Fix process_srcu()/srcu_batches_completed() datarace Date: Fri, 14 Feb 2020 16:29:31 -0800 Message-Id: <20200215002932.15976-3-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200215002907.GA15895@paulmck-ThinkPad-P72> References: <20200215002907.GA15895@paulmck-ThinkPad-P72> Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: "Paul E. McKenney" The srcu_struct structure's ->srcu_idx field is accessed locklessly, so reads must use READ_ONCE(). This commit therefore adds the needed READ_ONCE() invocation where it was missed. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney --- kernel/rcu/srcutree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 79848f7d..119a373 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -1079,7 +1079,7 @@ EXPORT_SYMBOL_GPL(srcu_barrier); */ unsigned long srcu_batches_completed(struct srcu_struct *ssp) { - return ssp->srcu_idx; + return READ_ONCE(ssp->srcu_idx); } EXPORT_SYMBOL_GPL(srcu_batches_completed); -- 2.9.5