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=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 3D01FC282C8 for ; Mon, 28 Jan 2019 17:26:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0B93720855 for ; Mon, 28 Jan 2019 17:26:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548696414; bh=d+T4q3J7C/K4rCY+5+UoUXcpQ11m0dOMCGOWeaKkp5A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=p9oUsZVAwK9jYGc1zAx3e8JVZASeubv0Qe3RbUzYb4EuFoGGtuIZaFuEr5whVQDXc RbpshzD/4mUv1INU5Ut+Bmm1DP6xtAFPKebSyJ+WmoaS0ubOPM6je/9ShAyEYI88CY AGrO9xE0wlc1F9XSNY3LYjid+axKe7qCe60/sBhQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731013AbfA1R0w (ORCPT ); Mon, 28 Jan 2019 12:26:52 -0500 Received: from mail.kernel.org ([198.145.29.99]:45812 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729294AbfA1QAb (ORCPT ); Mon, 28 Jan 2019 11:00:31 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (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 C464821848; Mon, 28 Jan 2019 16:00:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548691230; bh=d+T4q3J7C/K4rCY+5+UoUXcpQ11m0dOMCGOWeaKkp5A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DR8fOYaOlAyEqDt42Ufhln+oeOKiVeeYE/m9pvDmapIPzWqJs2Bo/5Gri+WuRBFFa rdW+nN/OZVmxcWjbXDX3WY2Ur7jwhcBaB1eHkwvKIl5sStwV0n4zWsl/Wee6miG/bg sXUHSeYElP30Cl6n1TIuyNFiKORyKp6VHkjtdFo4= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Paul E. McKenney" , Sasha Levin Subject: [PATCH AUTOSEL 4.19 024/258] srcu: Prevent __call_srcu() counter wrap with read-side critical section Date: Mon, 28 Jan 2019 10:55:30 -0500 Message-Id: <20190128155924.51521-24-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190128155924.51521-1-sashal@kernel.org> References: <20190128155924.51521-1-sashal@kernel.org> MIME-Version: 1.0 X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" [ Upstream commit 0607ba8403c4cdb253f8c5200ecf654dfb7790cc ] Ever since cdf7abc4610a ("srcu: Allow use of Tiny/Tree SRCU from both process and interrupt context"), it has been permissible to use SRCU read-side critical sections in interrupt context. This allows __call_srcu() to use SRCU read-side critical sections to prevent a new SRCU grace period from ending before the call to either srcu_funnel_gp_start() or srcu_funnel_exp_start completes, thus preventing SRCU grace-period counter overflow during that time. Note that this does not permit removal of the counter-wrap checks in srcu_gp_end(). These check are necessary to handle the case where a given CPU does not interact at all with SRCU for an extended time period. This commit therefore adds an SRCU read-side critical section to __call_srcu() in order to prevent grace period counter wrap during the funnel-locking process. Signed-off-by: Paul E. McKenney Signed-off-by: Sasha Levin --- kernel/rcu/srcutree.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 1ff17e297f0c..4b0a6e319b2c 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -853,6 +853,7 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, rcu_callback_t func, bool do_norm) { unsigned long flags; + int idx; bool needexp = false; bool needgp = false; unsigned long s; @@ -866,6 +867,7 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, return; } rhp->func = func; + idx = srcu_read_lock(sp); local_irq_save(flags); sdp = this_cpu_ptr(sp->sda); spin_lock_rcu_node(sdp); @@ -887,6 +889,7 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, srcu_funnel_gp_start(sp, sdp, s, do_norm); else if (needexp) srcu_funnel_exp_start(sp, sdp->mynode, s); + srcu_read_unlock(sp, idx); } /** -- 2.19.1