From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932750AbaHVRjN (ORCPT ); Fri, 22 Aug 2014 13:39:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10734 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932487AbaHVRjM (ORCPT ); Fri, 22 Aug 2014 13:39:12 -0400 Date: Fri, 22 Aug 2014 23:07:52 +0530 From: Amit Shah To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, riel@redhat.com, mingo@kernel.org, laijs@cn.fujitsu.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, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, sbw@mit.edu Subject: Re: [PATCH tip/core/rcu 1/2] rcu: Parallelize and economize NOCB kthread wakeups Message-ID: <20140822173752.GA25807@grmbl.mre> References: <20140813130049.GS4752@linux.vnet.ibm.com> <20140815052411.GF1934@grmbl.mre> <20140815150402.GD4752@linux.vnet.ibm.com> <20140818175345.GD31856@grmbl.mre> <20140819040149.GJ4752@linux.vnet.ibm.com> <20140822122453.GG16198@grmbl.mre> <20140822123651.GH16198@grmbl.mre> <20140822125649.GI16198@grmbl.mre> <20140822144819.GG2663@linux.vnet.ibm.com> <20140822171405.GJ16198@grmbl.mre> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140822171405.GJ16198@grmbl.mre> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (Fri) 22 Aug 2014 [22:44:05], Amit Shah wrote: > Hm, found it: > > The stall happens in do_initcalls(). > > pm_sysrq_init() is the function that causes the hang. When I #if 0 > the line > > register_sysrq_key('o', &sysrq_poweroff_op); > > in pm_sysrq_init(), the boot proceeds normally. > > Now what this is, and what relation this has to rcu and that patch in > particular is next... ... and enabling the following debug options makes the bug disappear: CONFIG_DEBUG_OBJECTS=y CONFIG_DEBUG_OBJECTS_SELFTEST=y CONFIG_DEBUG_OBJECTS_FREE=y CONFIG_DEBUG_OBJECTS_TIMERS=y CONFIG_DEBUG_OBJECTS_WORK=y CONFIG_DEBUG_OBJECTS_RCU_HEAD=y CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER=y CONFIG_DEBUG_OBJECTS_ENABLE_DEFAULT=1 Anyway, so it looks like a race somewhere in the schedule_work_on() chain. Not sure how to capture the debug messages there w/o disabling these debug options. I'll keep trying, though. Amit