linux-kernel - RE: [PATCH] genhd: Do not hold event lock when scheduling workqueue elements

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Date:   Tue, 7 Feb 2017 03:48:52 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Bart Van Assche <Bart.VanAssche@...disk.com>,
        "hare@...e.com" <hare@...e.com>, "hare@...e.de" <hare@...e.de>,
        "axboe@...nel.dk" <axboe@...nel.dk>
CC:     "hch@....de" <hch@....de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "jth@...nel.org" <jth@...nel.org>
Subject: RE: [PATCH] genhd: Do not hold event lock when scheduling workqueue
 elements

> From: Bart Van Assche [mailto:Bart.VanAssche@...disk.com]
>
> On Tue, 2017-02-07 at 02:23 +0000, Dexuan Cui wrote:
> > Any news on this thread?
> >
> > The issue is still blocking Linux from booting up normally in my test. :-(
> >
> > Have we identified the faulty patch?
> > If so, at least I can try to revert it to boot up.
>
> It's interesting that you have a reproducible testcase. If you can tell me how to
> reproduce this I'll have a look at it together with Hannes.
>
> Bart.

I'm running a Ubuntu 16.04 guest on Hyper-V with the guest kernel replaced
with the linux-next kernel.

I can boot the guest with linux-next's next-20170130 without any issue,
but since next-20170131 I haven't succeeded in booting the guest.

With next-20170203 (mentioned in my mail last Friday), I got the same
calltrace as Hannes.

With today's linux-next (next-20170206), actually the calltrace changed to
the below:

(Please see the attached files for the kernel config and the full kernel log.)
(I applied Hannes's patch in this thread, but the situation remained the same.)

[  121.824158] INFO: task systemd-udevd:91 blocked for more than 60 seconds.
[  121.854885]       Not tainted 4.10.0-rc6-next-20170206+ #1
[  121.885004] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  121.927618] systemd-udevd   D12816    91     86 0x00000000
[  121.952912] Call Trace:
[  121.964366]  __schedule+0x2a9/0x900
[  121.979931]  schedule+0x36/0x80
[  121.995288]  async_synchronize_cookie_domain+0x91/0x130
[  122.023036]  ? remove_wait_queue+0x70/0x70
[  122.051383]  async_synchronize_full+0x17/0x20
[  122.076925]  do_init_module+0xc1/0x1f9
[  122.097530]  load_module+0x24bc/0x2980
[  122.118418]  ? ref_module+0x1c0/0x1c0
[  122.139060]  SYSC_finit_module+0xbc/0xf0
[  122.161566]  SyS_finit_module+0xe/0x10
[  122.185397]  entry_SYSCALL_64_fastpath+0x1e/0xb2
[  122.221880] RIP: 0033:0x7f1d69105c19
[  122.248526] RSP: 002b:00007ffe34dc3928 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
[  122.283349] RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007f1d69105c19
[  122.315987] RDX: 0000000000000000 RSI: 00007f1d695fbe2a RDI: 000000000000000c
[  122.354369] RBP: 00007ffe34dc2930 R08: 0000000000000000 R09: 0000000000000000
[  122.407496] R10: 000000000000000c R11: 0000000000000246 R12: 000055f0b9b910a0
[  122.443667] R13: 00007ffe34dc2910 R14: 0000000000000005 R15: 000000000aba9500
[  122.475741]
[  122.475741] Showing all locks held in the system:
[  122.503742] 2 locks held by khungtaskd/17:
[  122.524260]  #0:  (rcu_read_lock){......}, at: [<ffffffff9a10d5f1>] watchdog+0xa1/0x3d0
[  122.569110]  #1:  (tasklist_lock){......}, at: [<ffffffff9a0aaf8d>] debug_show_all_locks+0x3d/0x1a0
[  122.623903] 2 locks held by kworker/u128:1/61:
[  122.654030]  #0:  ("events_unbound"){......}, at: [<ffffffff9a079035>] process_one_work+0x175/0x540
[  122.710469]  #1:  ((&entry->work)){......}, at: [<ffffffff9a079035>] process_one_work+0x175/0x540
[  122.770659]

Thanks,
-- Dexuan

Download attachment "kernel.config.zip" of type "application/x-zip-compressed" (22441 bytes)

Download attachment "putty.log.zip" of type "application/x-zip-compressed" (10588 bytes)