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 A2418C43603 for ; Tue, 10 Dec 2019 04:08:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 71C8C2071E for ; Tue, 10 Dec 2019 04:08:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575950890; bh=TvosYzjHhqHwTKEBhd/3tiZRrmMCcSiwrNi8S60IGbU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=g6vr4WLgMiXTDb4kqXJxLf0cjjw5HCVkVRa9xKCbd+yVaARhW1tL01Kea+0igmyFi csnuSpkOdXhW7SG05h+niUvVT5Hl6KBv7vc9CC5AYtOS6BHVTSEbEUSvinGr5rxP4w DBN/hGCyhOEcbf92/j6Jv5/fLm3DE5vNPAZ/rOw0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727222AbfLJEIJ (ORCPT ); Mon, 9 Dec 2019 23:08:09 -0500 Received: from mail.kernel.org ([198.145.29.99]:43570 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727036AbfLJEHt (ORCPT ); Mon, 9 Dec 2019 23:07:49 -0500 Received: from paulmck-ThinkPad-P72.home (199-192-87-166.static.wiline.com [199.192.87.166]) (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 EBE5321556; Tue, 10 Dec 2019 04:07:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575950869; bh=TvosYzjHhqHwTKEBhd/3tiZRrmMCcSiwrNi8S60IGbU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yoyQ2iWIecL42QowLXibFx2YW2D9EBEnB9jklhBXZvHES7f7issqAHIQ196Glny6x WT/VoesfY4Q17Nyaue71qZkt5hIVL/ZHF4ISdLYQDWaXu7rfiXrT8Ho0mgltEPAc2H 62+Y4wrN8ob/eLUFySOCqu2VbbjJI3t1bY2DMHsc= 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 09/12] srcu: Apply *_ONCE() to ->srcu_last_gp_end Date: Mon, 9 Dec 2019 20:07:38 -0800 Message-Id: <20191210040741.2943-9-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20191210040714.GA2715@paulmck-ThinkPad-P72> References: <20191210040714.GA2715@paulmck-ThinkPad-P72> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" The ->srcu_last_gp_end field is accessed from any CPU at any time by synchronize_srcu(), so non-initialization references need to use READ_ONCE() and WRITE_ONCE(). This commit therefore makes that change. Reported-by: syzbot+08f3e9d26e5541e1ecf2@syzkaller.appspotmail.com Acked-by: Marco Elver Signed-off-by: Paul E. McKenney --- kernel/rcu/srcutree.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 5dffade..21acdff 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -530,7 +530,7 @@ static void srcu_gp_end(struct srcu_struct *ssp) idx = rcu_seq_state(ssp->srcu_gp_seq); WARN_ON_ONCE(idx != SRCU_STATE_SCAN2); cbdelay = srcu_get_delay(ssp); - ssp->srcu_last_gp_end = ktime_get_mono_fast_ns(); + WRITE_ONCE(ssp->srcu_last_gp_end, ktime_get_mono_fast_ns()); rcu_seq_end(&ssp->srcu_gp_seq); gpseq = rcu_seq_current(&ssp->srcu_gp_seq); if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, gpseq)) @@ -762,6 +762,7 @@ static bool srcu_might_be_idle(struct srcu_struct *ssp) unsigned long flags; struct srcu_data *sdp; unsigned long t; + unsigned long tlast; /* If the local srcu_data structure has callbacks, not idle. */ local_irq_save(flags); @@ -780,9 +781,9 @@ static bool srcu_might_be_idle(struct srcu_struct *ssp) /* First, see if enough time has passed since the last GP. */ t = ktime_get_mono_fast_ns(); + tlast = READ_ONCE(ssp->srcu_last_gp_end); if (exp_holdoff == 0 || - time_in_range_open(t, ssp->srcu_last_gp_end, - ssp->srcu_last_gp_end + exp_holdoff)) + time_in_range_open(t, tlast, tlast + exp_holdoff)) return false; /* Too soon after last GP. */ /* Next, check for probable idleness. */ -- 2.9.5