From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755849Ab1FPMNf (ORCPT ); Thu, 16 Jun 2011 08:13:35 -0400 Received: from merlin.infradead.org ([205.233.59.134]:49851 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755854Ab1FPMNa convert rfc822-to-8bit (ORCPT ); Thu, 16 Jun 2011 08:13:30 -0400 Subject: Re: [PATCH 1/3] stop_machine: kill __stop_machine() From: Peter Zijlstra To: Tejun Heo Cc: x86@kernel.org, mingo@elte.hu, akpm@linux-foundation.org, torvalds@linux-foundation.org, suresh.b.siddha@intel.com, linux-kernel@vger.kernel.org In-Reply-To: <1308071218-5912-2-git-send-email-tj@kernel.org> References: <1308071218-5912-1-git-send-email-tj@kernel.org> <1308071218-5912-2-git-send-email-tj@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Thu, 16 Jun 2011 14:12:52 +0200 Message-ID: <1308226372.13240.42.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2011-06-14 at 19:06 +0200, Tejun Heo wrote: > +++ b/arch/x86/kernel/alternative.c > @@ -719,8 +719,7 @@ void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len) > tpp.nparams = 1; > atomic_set(&stop_machine_first, 1); > wrote_text = 0; > - /* Use __stop_machine() because the caller already got online_cpus. */ > - __stop_machine(stop_machine_text_poke, (void *)&tpp, cpu_online_mask); > + stop_machine(stop_machine_text_poke, (void *)&tpp, cpu_online_mask); > return addr; > } Please have a look at: --- commit d91309f69b7bdb64aeb30106fde8d18c5dd354b5 Author: Peter Zijlstra Date: Fri Feb 11 22:07:46 2011 +0100 x86: Fix text_poke_smp_batch() deadlock Fix this deadlock - we are already holding the mutex: ======================================================= [ INFO: possible circular locking dependency detected ] 2.6.38-rc4-test+ #1 ------------------------------------------------------- bash/1850 is trying to acquire lock: (text_mutex){+.+.+.}, at: [] return_to_handler+0x0/0x2f but task is already holding lock: (smp_alt){+.+...}, at: [] return_to_handler+0x0/0x2f which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (smp_alt){+.+...}: [] lock_acquire+0xcd/0xf8 [] __mutex_lock_common+0x4c/0x339 [] mutex_lock_nested+0x3e/0x43 [] alternatives_smp_switch+0x77/0x1d8 [] do_boot_cpu+0xd7/0x762 [] native_cpu_up+0xe6/0x16a [] _cpu_up+0x9d/0xee [] cpu_up+0xd3/0xe7 [] kernel_init+0xe8/0x20a [] kernel_thread_helper+0x4/0x10 -> #1 (cpu_hotplug.lock){+.+.+.}: [] lock_acquire+0xcd/0xf8 [] __mutex_lock_common+0x4c/0x339 [] mutex_lock_nested+0x3e/0x43 [] get_online_cpus+0x41/0x55 [] stop_machine+0x1e/0x3e [] text_poke_smp_batch+0x3a/0x3c [] arch_optimize_kprobes+0x10d/0x11c [] kprobe_optimizer+0x152/0x222 [] process_one_work+0x1d3/0x335 [] worker_thread+0x104/0x1a4 [] kthread+0x9d/0xa5 [] kernel_thread_helper+0x4/0x10 -> #0 (text_mutex){+.+.+.}: other info that might help us debug this: 6 locks held by bash/1850: #0: (&buffer->mutex){+.+.+.}, at: [] return_to_handler+0x0/0x2f #1: (s_active#75){.+.+.+}, at: [] return_to_handler+0x0/0x2f #2: (x86_cpu_hotplug_driver_mutex){+.+.+.}, at: [] return_to_handler+0x0/0x2f #3: (cpu_add_remove_lock){+.+.+.}, at: [] return_to_handler+0x0/0x2f #4: (cpu_hotplug.lock){+.+.+.}, at: [] return_to_handler+0x0/0x2f #5: (smp_alt){+.+...}, at: [] return_to_handler+0x0/0x2f stack backtrace: Pid: 1850, comm: bash Not tainted 2.6.38-rc4-test+ #1 Call Trace: [] print_circular_bug+0xa8/0xb7 [] mutex_lock_nested+0x3e/0x43 [] alternatives_smp_unlock+0x3d/0x93 [] alternatives_smp_switch+0x198/0x1d8 [] native_cpu_die+0x65/0x95 [] _cpu_down+0x13e/0x202 [] sysfs_write_file+0x108/0x144 [] vfs_write+0xac/0xff [] sys_write+0x4a/0x6e Reported-by: Steven Rostedt Tested-by: Steven Rostedt Signed-off-by: Peter Zijlstra Cc: mathieu.desnoyers@efficios.com Cc: rusty@rustcorp.com.au Cc: ananth@in.ibm.com Cc: masami.hiramatsu.pt@hitachi.com Cc: fweisbec@gmail.com Cc: jbeulich@novell.com Cc: jbaron@redhat.com Cc: mhiramat@redhat.com LKML-Reference: <1297458466.5226.93.camel@laptop> Signed-off-by: Ingo Molnar diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 1236085..7038b95 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -671,7 +671,7 @@ void __kprobes text_poke_smp_batch(struct text_poke_param *params, int n) atomic_set(&stop_machine_first, 1); wrote_text = 0; - stop_machine(stop_machine_text_poke, (void *)&tpp, NULL); + __stop_machine(stop_machine_text_poke, (void *)&tpp, NULL); } #if defined(CONFIG_DYNAMIC_FTRACE) || defined(HAVE_JUMP_LABEL)