linux-kernel - Re: cgroup: WARNING in cgroup_kill

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Message-ID: <CACT4Y+asv7gEEFvq1RunCwUE40mTobuqN_8ahwo9K-QaqP547w@mail.gmail.com>
Date:   Thu, 9 Mar 2017 10:48:28 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Zefan Li <lizefan@...wei.com>
Cc:     Tejun Heo <tj@...nel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>, jweiner@...com,
        LKML <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: cgroup: WARNING in cgroup_kill_sb

On Thu, Mar 9, 2017 at 10:24 AM, Zefan Li <lizefan@...wei.com> wrote:
> On 2017/3/3 3:15, Dmitry Vyukov wrote:
>> Hello,
>>
>> The following program triggers WARNING in cgroup_kill_sb:
>> https://gist.githubusercontent.com/dvyukov/47a37d3b899ece1f57e512dc6c90bca6/raw/250894f3d6e2954eed01bac39e4c3b7ec59a9c31/gistfile1.txt
>>
>>
>> WARNING: CPU: 2 PID: 3092 at lib/percpu-refcount.c:317
>> percpu_ref_kill_and_confirm+0x3ff/0x4f0 lib/percpu-refcount.c:316
>> percpu_ref_kill_and_confirm called more than once on css_release!
>> Kernel panic - not syncing: panic_on_warn set ...
>>
>> CPU: 2 PID: 3092 Comm: a.out Not tainted 4.10.0+ #260
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>> Call Trace:
>>  __dump_stack lib/dump_stack.c:15 [inline]
>>  dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
>>  panic+0x1fb/0x412 kernel/panic.c:179
>>  __warn+0x1c4/0x1e0 kernel/panic.c:540
>>  warn_slowpath_fmt+0xc5/0x100 kernel/panic.c:563
>>  percpu_ref_kill_and_confirm+0x3ff/0x4f0 lib/percpu-refcount.c:316
>>  percpu_ref_kill include/linux/percpu-refcount.h:119 [inline]
>>  cgroup_kill_sb+0x188/0x530 kernel/cgroup/cgroup.c:1833
>>  deactivate_locked_super+0x88/0xd0 fs/super.c:309
>>  deactivate_super+0x155/0x1b0 fs/super.c:340
>>  cleanup_mnt+0xb2/0x160 fs/namespace.c:1112
>>  __cleanup_mnt+0x16/0x20 fs/namespace.c:1119
>>  task_work_run+0x18a/0x260 kernel/task_work.c:116
>>  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
>>  exit_to_usermode_loop+0x23b/0x2a0 arch/x86/entry/common.c:160
>>  prepare_exit_to_usermode arch/x86/entry/common.c:190 [inline]
>>  syscall_return_slowpath+0x4d3/0x570 arch/x86/entry/common.c:259
>>  entry_SYSCALL_64_fastpath+0xc0/0xc2
>> RIP: 0033:0x440b39
>> RSP: 002b:00007f3e8bd0cdb8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
>> RAX: ffffffffffffffec RBX: 0000000000000000 RCX: 0000000000440b39
>> RDX: 00000000004a0f3b RSI: 00000000004a0f34 RDI: 00000000004a0f34
>> RBP: 00007f3e8bd0cdd0 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000005 R11: 0000000000000202 R12: 0000000000000000
>> R13: 0000000000000000 R14: 00007f3e8bd0d9c0 R15: 00007f3e8bd0d700
>>
>> On commit 4977ab6e92e267afe9d8f78438c3db330ca8434c
>> .
>
> could you share your kernel config? I can't reproduce this bug.

It's attached to the previous email.

Run the repro for longer, it's some kind of race.