From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f41.google.com (mail-pb0-f41.google.com [209.85.160.41]) by kanga.kvack.org (Postfix) with ESMTP id E73B26B0031 for ; Wed, 27 Nov 2013 01:39:00 -0500 (EST) Received: by mail-pb0-f41.google.com with SMTP id jt11so9774986pbb.28 for ; Tue, 26 Nov 2013 22:39:00 -0800 (PST) Received: from szxga02-in.huawei.com (szxga02-in.huawei.com. [119.145.14.65]) by mx.google.com with ESMTPS id sg3si32877646pbb.103.2013.11.26.22.38.56 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 26 Nov 2013 22:38:59 -0800 (PST) Message-ID: <52959328.3090407@huawei.com> Date: Wed, 27 Nov 2013 14:37:28 +0800 From: Li Zefan MIME-Version: 1.0 Subject: Re: [PATCH] cpuset: Fix memory allocator deadlock References: <20131126140341.GL10022@twins.programming.kicks-ass.net> In-Reply-To: <20131126140341.GL10022@twins.programming.kicks-ass.net> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: Tejun Heo , John Stultz , Mel Gorman , Juri Lelli , linux-kernel@vger.kernel.org, linux-mm@kvack.org On 2013/11/26 22:03, Peter Zijlstra wrote: > 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(). > Yeah, the other one in set_mems_allowed() was fixed by John. > 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 Acked-by: Li Zefan -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org