From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755287Ab0IWNbN (ORCPT ); Thu, 23 Sep 2010 09:31:13 -0400 Received: from mtagate6.uk.ibm.com ([194.196.100.166]:38509 "EHLO mtagate6.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751749Ab0IWNbL (ORCPT ); Thu, 23 Sep 2010 09:31:11 -0400 Date: Thu, 23 Sep 2010 15:31:03 +0200 From: Heiko Carstens To: Peter Zijlstra Cc: Tejun Heo , Thomas Gleixner , Ingo Molnar , Andrew Morton , Rusty Russell , linux-kernel@vger.kernel.org, Arnd Bergmann Subject: Re: [PATCH/RFC] timer: fix deadlock on cpu hotplug Message-ID: <20100923133103.GA3832@osiris.boeblingen.de.ibm.com> References: <20100921142017.GA2291@osiris.boeblingen.de.ibm.com> <4C98D0EB.30002@kernel.org> <1285083618.2275.884.camel@laptop> <20100922083706.GA2177@osiris.boeblingen.de.ibm.com> <1285147362.2275.896.camel@laptop> <1285165776.2275.1022.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1285165776.2275.1022.camel@laptop> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 22, 2010 at 04:29:36PM +0200, Peter Zijlstra wrote: > On Wed, 2010-09-22 at 11:22 +0200, Peter Zijlstra wrote: > > > The idea was to move it to a class of its own above SCHED_FIFO. > > > > I'll try and get something done, but I'm heading out to LinuxCon.JP > > soon. > > Something like the below, it seems to boot, build a kernel and hotplug. Thanks for the fast patch. Yes, it works. Sort of: ------------[ cut here ]------------ WARNING: at kernel/kthread.c:182 Modules linked in: Modules linked in: CPU: 0 Not tainted 2.6.36-rc5-00034-g8b15575-dirty #21 Process cpukill2.sh (pid: 2630, task: 000000003ac05238, ksp: 000000003d8bf8d8) Krnl PSW : 0704000180000000 000000000016adb6 (kthread_bind+0x8a/0x98) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:0 CC:0 PM:0 EA:3 Krnl GPRS: 0000000000000000 00000000026afd00 0000000000000000 0000000000000002 000000000016ad60 000000000050e980 0000000000000000 00000000026b9150 0000000000000002 0000000000000002 0000000000000002 000000003fbc0138 0000000000000002 000000000050eb08 000000000016ad60 000000003d8bfbb0 Krnl Code: 000000000016ada6: f0b80004ebbf srp 4(12,%r0),3007(%r14),8 000000000016adac: f0a0000407f4 srp 4(11,%r0),2036,0 000000000016adb2: a7f40001 brc 15,16adb4 >000000000016adb6: e340f0b80004 lg %r4,184(%r15) 000000000016adbc: ebbff0a00004 lmg %r11,%r15,160(%r15) 000000000016adc2: 07f4 bcr 15,%r4 000000000016adc4: eb5ff0400024 stmg %r5,%r15,64(%r15) 000000000016adca: c0d0001d1ea3 larl %r13,50eb10 Call Trace: ([<000000000016ad60>] kthread_bind+0x34/0x98) [<00000000004f5270>] cpu_stop_cpu_callback+0xf0/0x1e4 [<00000000004ff806>] notifier_call_chain+0x8e/0xdc [<00000000001721f2>] __raw_notifier_call_chain+0x22/0x30 [<0000000000148c68>] __cpu_notify+0x44/0x80 [<00000000004f3be0>] _cpu_up+0x110/0x150 [<00000000004f3cea>] cpu_up+0xca/0xec [<00000000004f0416>] store_online+0x92/0xcc [<000000000026880a>] sysfs_write_file+0xf6/0x1a8 [<00000000001f8c6c>] vfs_write+0xb0/0x158 [<00000000001f8f6c>] SyS_write+0x58/0xa8 [<0000000000117cf6>] sysc_noemu+0x10/0x16 [<0000020000158fcc>] 0x20000158fcc 4 locks held by cpukill2.sh/2630: #0: (&buffer->mutex){+.+.+.}, at: [<000000000026875e>] sysfs_write_file+0x4a/0x1a8 #1: (s_active#66){.+.+.+}, at: [<00000000002687e6>] sysfs_write_file+0xd2/0x1a80 #2: (cpu_add_remove_lock){+.+.+.}, at: [<00000000004f3cce>] cpu_up+0xae/0xec #3: (cpu_hotplug.lock){+.+.+.}, at: [<0000000000148d42>] cpu_hotplug_begin+0x3e/0x74 Last Breaking-Event-Address: [<000000000016adb2>] kthread_bind+0x86/0x98 ..and crashes afterwards ;) Btw. I also tried to boot 2.6.35.5 with your patch and it hangs just at the beginning. I also had to apply 5e3d20a68f63fc5a310687d81956c3b96e488b84 "init: Remove the BKL from startup code" to make the machine boot again, which was a bit surprising.