From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756325AbaHVM6J (ORCPT ); Fri, 22 Aug 2014 08:58:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:6223 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756094AbaHVM6H (ORCPT ); Fri, 22 Aug 2014 08:58:07 -0400 Date: Fri, 22 Aug 2014 18:26:49 +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: <20140822125649.GI16198@grmbl.mre> References: <20140812213936.GA3106@linux.vnet.ibm.com> <20140812214151.GB3106@linux.vnet.ibm.com> <20140813054439.GA29913@grmbl.mre> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140822123651.GH16198@grmbl.mre> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (Fri) 22 Aug 2014 [18:06:51], Amit Shah wrote: > On (Fri) 22 Aug 2014 [17:54:53], Amit Shah wrote: > > On (Mon) 18 Aug 2014 [21:01:49], Paul E. McKenney wrote: > > > > > The odds are low over the next few days. I am adding nastier rcutorture > > > testing, however. It would still be very good to get debug information > > > from your setup. One approach would be to convert the trace function > > > calls into printk(), if that would help. > > > > I added a few printks on the lines of the traces in cases where > > rcu_nocb_poll was checked -- since that reproduces the hang. Are the > > following traces sufficient, or should I keep adding more printks? > > > > In the case of rcu-trace-nopoll.txt, the messages stop after a while > > (when the guest locks up hard). That's when I kill the qemu process. > > And this is bt from gdb when the endless > > RCUDEBUG __call_rcu_nocb_enqueue 2146 rcu_preempt 0 WakeNot > > messages are being spewed. > > I can't time it, but hope it gives some indication along with the printks. ... and after the system 'locks up', this is the state it's in: ^C Program received signal SIGINT, Interrupt. native_safe_halt () at ./arch/x86/include/asm/irqflags.h:50 50 } (gdb) bt #0 native_safe_halt () at ./arch/x86/include/asm/irqflags.h:50 #1 0xffffffff8100b9c1 in arch_safe_halt () at ./arch/x86/include/asm/paravirt.h:111 #2 default_idle () at arch/x86/kernel/process.c:311 #3 0xffffffff8100c107 in arch_cpu_idle () at arch/x86/kernel/process.c:302 #4 0xffffffff8106a25a in cpuidle_idle_call () at kernel/sched/idle.c:120 #5 cpu_idle_loop () at kernel/sched/idle.c:220 #6 cpu_startup_entry (state=) at kernel/sched/idle.c:268 #7 0xffffffff813e068b in rest_init () at init/main.c:418 #8 0xffffffff81a8cf5a in start_kernel () at init/main.c:680 #9 0xffffffff81a8c4ba in x86_64_start_reservations (real_mode_data=) at arch/x86/kernel/head64.c:193 #10 0xffffffff81a8c607 in x86_64_start_kernel (real_mode_data=0x13f90 ) at arch/x86/kernel/head64.c:182 #11 0x0000000000000000 in ?? () Wondering why it's doing this. Am stepping through cpu_startup_entry() to see if I get any clues. Amit