From patchwork Wed Nov 2 20:30:30 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 4899 Return-Path: X-Original-To: patchwork@peony.canonical.com Delivered-To: patchwork@peony.canonical.com Received: from fiordland.canonical.com (fiordland.canonical.com [91.189.94.145]) by peony.canonical.com (Postfix) with ESMTP id E3C2123DC3 for ; Wed, 2 Nov 2011 20:31:21 +0000 (UTC) Received: from mail-fx0-f52.google.com (mail-fx0-f52.google.com [209.85.161.52]) by fiordland.canonical.com (Postfix) with ESMTP id D8808A1867A for ; Wed, 2 Nov 2011 20:31:21 +0000 (UTC) Received: by mail-fx0-f52.google.com with SMTP id n26so1195523faa.11 for ; Wed, 02 Nov 2011 13:31:21 -0700 (PDT) Received: by 10.223.16.82 with SMTP id n18mr10871038faa.2.1320265881633; Wed, 02 Nov 2011 13:31:21 -0700 (PDT) X-Forwarded-To: linaro-patchwork@canonical.com X-Forwarded-For: patch@linaro.org linaro-patchwork@canonical.com Delivered-To: patches@linaro.org Received: by 10.152.14.103 with SMTP id o7cs64009lac; Wed, 2 Nov 2011 13:31:21 -0700 (PDT) Received: by 10.52.112.74 with SMTP id io10mr6062491vdb.116.1320265879006; Wed, 02 Nov 2011 13:31:19 -0700 (PDT) Received: from e4.ny.us.ibm.com (e4.ny.us.ibm.com. [32.97.182.144]) by mx.google.com with ESMTPS id c10si853698vcp.52.2011.11.02.13.31.18 (version=TLSv1/SSLv3 cipher=OTHER); Wed, 02 Nov 2011 13:31:19 -0700 (PDT) Received-SPF: pass (google.com: domain of paulmck@linux.vnet.ibm.com designates 32.97.182.144 as permitted sender) client-ip=32.97.182.144; Authentication-Results: mx.google.com; spf=pass (google.com: domain of paulmck@linux.vnet.ibm.com designates 32.97.182.144 as permitted sender) smtp.mail=paulmck@linux.vnet.ibm.com Received: from /spool/local by e4.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 2 Nov 2011 16:31:04 -0400 Received: from d01relay01.pok.ibm.com ([9.56.227.233]) by e4.ny.us.ibm.com ([192.168.1.104]) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Wed, 2 Nov 2011 16:31:02 -0400 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay01.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id pA2KV1pL135178 for ; Wed, 2 Nov 2011 16:31:01 -0400 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id pA2KUrXG029937 for ; Wed, 2 Nov 2011 16:31:01 -0400 Received: from paulmck-ThinkPad-W500 (sig-9-49-130-61.mts.ibm.com [9.49.130.61]) by d01av04.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id pA2KUqAL029871; Wed, 2 Nov 2011 16:30:53 -0400 Received: by paulmck-ThinkPad-W500 (Postfix, from userid 1000) id CCC06EA9F9; Wed, 2 Nov 2011 13:30:51 -0700 (PDT) From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, patches@linaro.org, "Paul E. McKenney" Subject: [PATCH RFC tip/core/rcu 09/28] rcu: Document failing tick as cause of RCU CPU stall warning Date: Wed, 2 Nov 2011 13:30:30 -0700 Message-Id: <1320265849-5744-9-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.3.2 In-Reply-To: <20111102203017.GA3830@linux.vnet.ibm.com> References: <20111102203017.GA3830@linux.vnet.ibm.com> x-cbid: 11110220-3534-0000-0000-0000012AA3C7 One of lclaudio's systems was seeing RCU CPU stall warnings from idle. These turned out to be caused by a bug that stopped scheduling-clock tick interrupts from being sent to a given CPU for several hundred seconds. This commit therefore updates the documentation to call this out as a possible cause for RCU CPU stall warnings. Signed-off-by: Paul E. McKenney --- Documentation/RCU/stallwarn.txt | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-) diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt index 4e95920..f3e0625 100644 --- a/Documentation/RCU/stallwarn.txt +++ b/Documentation/RCU/stallwarn.txt @@ -101,6 +101,11 @@ o A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that CONFIG_TREE_PREEMPT_RCU case, you might see stall-warning messages. +o A hardware or software issue shuts off the scheduler-clock + interrupt on a CPU that is not in dyntick-idle mode. This + problem really has happened, and seems to be most likely to + result in RCU CPU stall warnings for CONFIG_NO_HZ=n kernels. + o A bug in the RCU implementation. o A hardware failure. This is quite unlikely, but has occurred