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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 C8F6AC433EF for ; Wed, 15 Sep 2021 23:33:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A0A11611C1 for ; Wed, 15 Sep 2021 23:33:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232990AbhIOXfF (ORCPT ); Wed, 15 Sep 2021 19:35:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:60342 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232897AbhIOXfE (ORCPT ); Wed, 15 Sep 2021 19:35:04 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id F073A61131; Wed, 15 Sep 2021 23:33:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1631748825; bh=G+c4Zp8HyyHDC/1xdbUnO8ByLENVGrEKTMyNI4qVzWE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BYUXyzJ/NtJzKizIQxFPc9eLRMx9wieHozd9y50kElSnHAcg1Y9zjI25+XG9/P1Y/ RZPGDLAQqVnS3hlFUSBmTTIW7uW0/Ic5NgSLv3gJuMGRW5K/la5W2t/DqRZE6fpj1G p8U2lLbVRXZU6B+5VbICp6toK+mFLj68K9uUqgpLjz9QQvMjxqmO0Dh9XtA7nIco2Y McZOUCCIM2X8EGIEFyJeGtfSo18FB+KQss346kPab4MK8pvTncNHv9zfkurEwPdnD7 tnbMC9huS/Xo5aRkH5YJztGePk7poQFxjRaNOB3iQmb/UxF9aMxghiqXqBBJXrNONC /UUqzkMhG373Q== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id C30D15C0926; Wed, 15 Sep 2021 16:33:44 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.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 rcu 05/14] doc: Add another stall-warning root cause in stallwarn.rst Date: Wed, 15 Sep 2021 16:33:34 -0700 Message-Id: <20210915233343.3906738-5-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20210915233305.GA3906641@paulmck-ThinkPad-P17-Gen-1> References: <20210915233305.GA3906641@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org This commit adds a bullet item noting that both deficiencies and surpluses of calls to rcu_*_enter() and rcu_*_exit() can result in RCU CPU stall warnings. Signed-off-by: Paul E. McKenney --- Documentation/RCU/stallwarn.rst | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst index 5036df24ae61..28f8ad16db25 100644 --- a/Documentation/RCU/stallwarn.rst +++ b/Documentation/RCU/stallwarn.rst @@ -96,6 +96,16 @@ warnings: the ``rcu_.*timer wakeup didn't happen for`` console-log message, which will include additional debugging information. +- A low-level kernel issue that either fails to invoke one of the + variants of rcu_user_enter(), rcu_user_exit(), rcu_idle_enter(), + rcu_idle_exit(), rcu_irq_enter(), or rcu_irq_exit() on the one + hand, or that invokes one of them too many times on the other. + Historically, the most frequent issue has been an omission + of either irq_enter() or irq_exit(), which in turn invoke + rcu_irq_enter() or rcu_irq_exit(), respectively. Building your + kernel with CONFIG_RCU_EQS_DEBUG=y can help track down these types + of issues, which sometimes arise in architecture-specific code. + - A bug in the RCU implementation. - A hardware failure. This is quite unlikely, but has occurred -- 2.31.1.189.g2e36527f23