Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753813AbaBOUSI (ORCPT ); Sat, 15 Feb 2014 15:18:08 -0500 Received: from mail-pb0-f52.google.com ([209.85.160.52]:35468 "EHLO mail-pb0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753608AbaBOUSG (ORCPT ); Sat, 15 Feb 2014 15:18:06 -0500 Message-ID: <52FFCB70.3090600@gmail.com> Date: Sun, 16 Feb 2014 04:17:52 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: Fengguang Wu , Tejun Heo CC: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [cgroups] BUG: unable to handle kernel NULL pointer dereference at 0000003c References: <20140215124212.GA8782@localhost> In-Reply-To: <20140215124212.GA8782@localhost> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 于 2014年02月15日 20:42, Fengguang Wu 写道: > Greetings, > > I got the below dmesg and the first bad commit is > > git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git for-next > commit de00ffa56ea3132c6013fc8f07133b8a1014cf53 > Author: Tejun Heo > AuthorDate: Tue Feb 11 11:52:48 2014 -0500 > Commit: Tejun Heo > CommitDate: Tue Feb 11 11:52:48 2014 -0500 > > cgroup: make cgroup_subsys->base_cftypes use cgroup_add_cftypes() > > Currently, cgroup_subsys->base_cftypes registration is different from > dynamic cftypes registartion. Instead of going through > cgroup_add_cftypes(), cgroup_init_subsys() invokes > cgroup_init_cftsets() which makes use of cgroup_subsys->base_cftset > which doesn't involve dynamic allocation. > > While avoiding dynamic allocation is somewhat nice, having two > separate paths for cftypes registration is nasty, especially as we're > planning to add more operations during cftypes registration. > > This patch drops cgroup_init_cftsets() and cgroup_subsys->base_cftset > and registers base_cftypes using cgroup_add_cftypes(). This is done > as a separate step in cgroup_init() instead of a part of > cgroup_init_subsys(). This is because cgroup_init_subsys() can be > called very early during boot when kmalloc() isn't available yet. > > Signed-off-by: Tejun Heo > Acked-by: Li Zefan > > [ 0.020000] Calibrating delay loop (skipped) preset value.. 5786.00 BogoMIPS (lpj=28930000) > [ 0.020000] pid_max: default: 32768 minimum: 301 > [ 0.020000] Mount-cache hash table entries: 512 > [ 0.020000] BUG: unable to handle kernel NULL pointer dereference at 0000003c > [ 0.020000] IP: [] cgroup_cfts_commit+0x27/0x1c1 > [ 0.020000] *pdpt = 0000000000000000 *pde = f000ff53f000ff53 > [ 0.020000] Oops: 0000 [#1] SMP > [ 0.020000] Modules linked in: > [ 0.020000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.14.0-rc2-next-20140212-02521-g4602175 #1 > [ 0.020000] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > [ 0.020000] task: cd497910 ti: cd492000 task.ti: cd492000 > [ 0.020000] EIP: 0060:[] EFLAGS: 00210282 CPU: 0 > [ 0.020000] EIP is at cgroup_cfts_commit+0x27/0x1c1 > [ 0.020000] EAX: cd4b1d0c EBX: cf004fa0 ECX: 00000001 EDX: 00000001 > [ 0.020000] ESI: 00000000 EDI: cd9820d4 EBP: cd493fa4 ESP: cd493f70 > [ 0.020000] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 > [ 0.020000] CR0: 8005003b CR2: 0000003c CR3: 0d96e000 CR4: 000006b0 > [ 0.020000] Stack: > [ 0.020000] cf004fa0 cd4b1d4c 00200246 cd9820d4 cc9d1129 0190c691 0000000c 000080d0 > [ 0.020000] cd493f90 cd493f90 cf004fa0 cd9820d4 cd4accc4 cd493fbc cc90c6fc 00000000 > [ 0.020000] 00000000 00000000 cd970800 cd493fcc cd78b646 00000000 00020800 cd493fe8 > [ 0.020000] Call Trace: > [ 0.020000] [] ? kmem_cache_alloc_trace+0x33f/0x3b7 > [ 0.020000] [] cgroup_add_cftypes+0x8f/0xca > [ 0.020000] [] cgroup_init+0x6a/0x26a > [ 0.020000] [] start_kernel+0x4d7/0x57a > [ 0.020000] [] i386_start_kernel+0x92/0x96 > [ 0.020000] Code: 5e 5f 5d c3 55 89 e5 57 56 53 83 ec 28 e8 94 ab 71 00 89 c7 8b 77 50 89 45 d8 8d 45 ec 89 45 ec 89 45 f0 b8 0c 1d 4b cd 88 55 e3 <8b> 5e 3c e8 c9 4d 71 00 85 ff 74 0e 31 c0 81 7e 3c c8 43 ec cd > [ 0.020000] EIP: [] cgroup_cfts_commit+0x27/0x1c1 SS:ESP 0068:cd493f70 > [ 0.020000] CR2: 000000000000003c > [ 0.020000] ---[ end trace fd4743fe17bdbf8e ]--- > [ 0.020000] Kernel panic - not syncing: Fatal exception > This is a corner case. If CGROUP_SCHED=y but FAIR_GROUP_SCHED=n && CFS_BANDWIDTH=n && RT_GROUP_SCHED=n: static struct cftype cpu_files[] = { { } /* terminate */ }; Should be fixed by the following change. Will test it and send out a formal patch on Monday. It's 4 a.m on Sunday, and I lose sleep. :( --- diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 851251b..fa393d84 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2348,6 +2348,9 @@ int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) { int ret; + if (!cfts || cfts[0].name[0] == '\0') + return 0; + ret = cgroup_init_cftypes(ss, cfts); if (ret) return ret; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/