From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161915Ab3LFOH1 (ORCPT ); Fri, 6 Dec 2013 09:07:27 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:43828 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161347Ab3LFNA4 (ORCPT ); Fri, 6 Dec 2013 08:00:56 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: John Stultz , Mel Gorman , Peter Zijlstra , Tejun Heo , Luis Henriques Subject: [PATCH 3.11 063/272] cpuset: Fix memory allocator deadlock Date: Fri, 6 Dec 2013 12:55:52 +0000 Message-Id: <1386334761-25517-64-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1386334761-25517-1-git-send-email-luis.henriques@canonical.com> References: <1386334761-25517-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.11.10.1 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra commit 0fc0287c9ed1ffd3706f8b4d9b314aa102ef1245 upstream. Juri hit the below lockdep report: [ 4.303391] ====================================================== [ 4.303392] [ INFO: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected ] [ 4.303394] 3.12.0-dl-peterz+ #144 Not tainted [ 4.303395] ------------------------------------------------------ [ 4.303397] kworker/u4:3/689 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: [ 4.303399] (&p->mems_allowed_seq){+.+...}, at: [] new_slab+0x6c/0x290 [ 4.303417] [ 4.303417] and this task is already holding: [ 4.303418] (&(&q->__queue_lock)->rlock){..-...}, at: [] blk_execute_rq_nowait+0x5b/0x100 [ 4.303431] which would create a new lock dependency: [ 4.303432] (&(&q->__queue_lock)->rlock){..-...} -> (&p->mems_allowed_seq){+.+...} [ 4.303436] [ 4.303898] the dependencies between the lock to be acquired and SOFTIRQ-irq-unsafe lock: [ 4.303918] -> (&p->mems_allowed_seq){+.+...} ops: 2762 { [ 4.303922] HARDIRQ-ON-W at: [ 4.303923] [] __lock_acquire+0x65a/0x1ff0 [ 4.303926] [] lock_acquire+0x93/0x140 [ 4.303929] [] kthreadd+0x86/0x180 [ 4.303931] [] ret_from_fork+0x7c/0xb0 [ 4.303933] SOFTIRQ-ON-W at: [ 4.303933] [] __lock_acquire+0x68c/0x1ff0 [ 4.303935] [] lock_acquire+0x93/0x140 [ 4.303940] [] kthreadd+0x86/0x180 [ 4.303955] [] ret_from_fork+0x7c/0xb0 [ 4.303959] INITIAL USE at: [ 4.303960] [] __lock_acquire+0x344/0x1ff0 [ 4.303963] [] lock_acquire+0x93/0x140 [ 4.303966] [] kthreadd+0x86/0x180 [ 4.303969] [] ret_from_fork+0x7c/0xb0 [ 4.303972] } Which reports that we take mems_allowed_seq with interrupts enabled. A little digging found that this can only be from cpuset_change_task_nodemask(). This is an actual deadlock because an interrupt doing an allocation will hit get_mems_allowed()->...->__read_seqcount_begin(), which will spin forever waiting for the write side to complete. Cc: John Stultz Cc: Mel Gorman Reported-by: Juri Lelli Signed-off-by: Peter Zijlstra Tested-by: Juri Lelli Acked-by: Li Zefan Acked-by: Mel Gorman Signed-off-by: Tejun Heo Signed-off-by: Luis Henriques --- kernel/cpuset.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/cpuset.c b/kernel/cpuset.c index ea1966d..b49f24a 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -1044,8 +1044,10 @@ static void cpuset_change_task_nodemask(struct task_struct *tsk, need_loop = task_has_mempolicy(tsk) || !nodes_intersects(*newmems, tsk->mems_allowed); - if (need_loop) + if (need_loop) { + local_irq_disable(); write_seqcount_begin(&tsk->mems_allowed_seq); + } nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems); mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP1); @@ -1053,8 +1055,10 @@ static void cpuset_change_task_nodemask(struct task_struct *tsk, mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP2); tsk->mems_allowed = *newmems; - if (need_loop) + if (need_loop) { write_seqcount_end(&tsk->mems_allowed_seq); + local_irq_enable(); + } task_unlock(tsk); } -- 1.8.3.2