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Re: WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738 __might_sleep+0x69/0x7e

Started byTejun Heo <tj@kernel.org>
First post2016-12-12 23:10 +0100
Last post2016-12-21 22:00 +0100
Articles 5 — 3 participants

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  Re: WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738  __might_sleep+0x69/0x7e Tejun Heo <tj@kernel.org> - 2016-12-12 23:10 +0100
    Re: WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738 __might_sleep+0x69/0x7e Cong Wang <xiyou.wangcong@gmail.com> - 2016-12-12 23:40 +0100
    Re: WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738  __might_sleep+0x69/0x7e Michal Hocko <mhocko@kernel.org> - 2016-12-21 11:50 +0100
      Re: WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738 __might_sleep+0x69/0x7e Cong Wang <xiyou.wangcong@gmail.com> - 2016-12-21 20:30 +0100
        Re: WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738  __might_sleep+0x69/0x7e Michal Hocko <mhocko@kernel.org> - 2016-12-21 22:00 +0100

#1540693 — Re: WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738 __might_sleep+0x69/0x7e

FromTejun Heo <tj@kernel.org>
Date2016-12-12 23:10 +0100
SubjectRe: WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738 __might_sleep+0x69/0x7e
Message-ID<sNGXf-1pE-9@gated-at.bofh.it>
Hello, Michal.

On Fri, Dec 09, 2016 at 04:12:29PM +0100, Michal Hocko wrote:
> Hi Tejun,
> I am seeing the following warning during boot in my kvm testing
> environment:
> [    3.549649] WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738 __might_sleep+0x69/0x7e
> [    3.551279] do not call blocking ops when !TASK_RUNNING; state=2 set at [<ffffffff81098621>] prepare_to_wait+0x65/0xac
> [    3.553354] Modules linked in:
> [    3.554032] CPU: 3 PID: 1568 Comm: modprobe Not tainted 4.9.0-rc8-nofstest5-next-20161209-00013-g3134766e941a #1018
> [    3.556099] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-20161025_171302-gandalf 04/01/2014
> [    3.557330] Call Trace:
> [    3.557330]  dump_stack+0x68/0x92
> [    3.557330]  __warn+0xc2/0xdd
> [    3.557330]  warn_slowpath_fmt+0x4b/0x53
> [    3.557330]  ? prepare_to_wait+0x65/0xac
> [    3.557330]  ? prepare_to_wait+0x65/0xac
> [    3.557330]  __might_sleep+0x69/0x7e
> [    3.557330]  do_ide_request+0x47/0x540
> [    3.557330]  ? __lock_is_held+0x47/0x7a
> [    3.557330]  ? hrtimer_try_to_cancel+0x15f/0x1c6
> [    3.557330]  ? _raw_spin_unlock_irqrestore+0x4c/0x61
> [    3.557330]  __blk_run_queue+0x31/0x3a
> [    3.557330]  cfq_insert_request+0x331/0x429
> [    3.557330]  __elv_add_request+0x2bb/0x346
> [    3.557330]  blk_flush_plug_list+0x1da/0x21f
> [    3.557330]  ? bit_wait+0x50/0x50
> [    3.557330]  io_schedule_timeout+0x47/0x102
> [    3.557330]  bit_wait_io+0x1b/0x5a
> [    3.557330]  __wait_on_bit+0x4d/0x7b
> [    3.557330]  out_of_line_wait_on_bit+0x72/0x7d
> [    3.557330]  ? bit_wait+0x50/0x50
> [    3.557330]  ? autoremove_wake_function+0x4e/0x4e
> [    3.557330]  __wait_on_buffer+0x40/0x43
> [    3.557330]  bh_submit_read+0x60/0x72
> [    3.557330]  ext4_get_branch+0x91/0x115
> [    3.557330]  ext4_ind_map_blocks+0x181/0xa16
> [    3.557330]  ? __lock_is_held+0x47/0x7a
> [    3.557330]  ? lock_acquire+0x133/0x1c7
> [    3.557330]  ext4_map_blocks+0x120/0x4ca
> [    3.557330]  ext4_mpage_readpages+0x2a7/0x70a
> [    3.557330]  ext4_readpages+0x33/0x35
> [    3.557330]  __do_page_cache_readahead+0x239/0x32a
> [    3.557330]  filemap_fault+0x180/0x602
> [    3.557330]  ? filemap_fault+0x180/0x602
> [    3.557330]  ext4_filemap_fault+0x37/0x4b
> [    3.557330]  __do_fault+0x1f/0x94
> [    3.557330]  handle_mm_fault+0x946/0xfca
> [    3.557330]  __do_page_fault+0x361/0x518
> [    3.557330]  do_page_fault+0x42/0x5f
> [    3.557330]  page_fault+0x22/0x30
> 
> At first I thought this would be related to you recent work
> http://lkml.kernel.org/r/1477673892-28940-1-git-send-email-tj@kernel.org
> but that doesn't seem to be in the linux-next I am using as a base.
> io_schedule_timeout is on the stack though so you might have an idea
> what is going on here. That might_sleep check has been added a long ago
> 02e7cf8f8488 ("ide-cd,atapi: use bio for internal commands") in 2.6.31
> so I am wondering what has changed since than.

10d784eae2b4 ("sched: always use blk_schedule_flush_plug in
io_schedule_out") seems related.  might_sleep is complaining that it's
being called while !TASK_RUNNING.  Shaohua, any ideas?

Thanks.

-- 
tejun

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#1540714 — Re: WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738 __might_sleep+0x69/0x7e

FromCong Wang <xiyou.wangcong@gmail.com>
Date2016-12-12 23:40 +0100
SubjectRe: WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738 __might_sleep+0x69/0x7e
Message-ID<sNHqi-1zl-19@gated-at.bofh.it>
In reply to#1540693
On Mon, Dec 12, 2016 at 2:03 PM, Tejun Heo <tj@kernel.org> wrote:
> Hello, Michal.
>
> On Fri, Dec 09, 2016 at 04:12:29PM +0100, Michal Hocko wrote:
>> At first I thought this would be related to you recent work
>> http://lkml.kernel.org/r/1477673892-28940-1-git-send-email-tj@kernel.org
>> but that doesn't seem to be in the linux-next I am using as a base.
>> io_schedule_timeout is on the stack though so you might have an idea
>> what is going on here. That might_sleep check has been added a long ago
>> 02e7cf8f8488 ("ide-cd,atapi: use bio for internal commands") in 2.6.31
>> so I am wondering what has changed since than.
>
> 10d784eae2b4 ("sched: always use blk_schedule_flush_plug in
> io_schedule_out") seems related.  might_sleep is complaining that it's
> being called while !TASK_RUNNING.  Shaohua, any ideas?

Yeah, it is pretty much similar to the one I fixed for networking:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d9dc8b0f8b4ec8cdc48ad5a20a3105387138be82

But in your case, it is complicated because of the wait bits API.

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#1545714

FromMichal Hocko <mhocko@kernel.org>
Date2016-12-21 11:50 +0100
Message-ID<sQMD7-2fN-19@gated-at.bofh.it>
In reply to#1540693
On Mon 12-12-16 14:45:31, Shaohua Li wrote:
> On Mon, Dec 12, 2016 at 05:03:49PM -0500, Tejun Heo wrote:
> > Hello, Michal.
> > 
> > On Fri, Dec 09, 2016 at 04:12:29PM +0100, Michal Hocko wrote:
> > > Hi Tejun,
> > > I am seeing the following warning during boot in my kvm testing
> > > environment:
> > > [    3.549649] WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738 __might_sleep+0x69/0x7e
> > > [    3.551279] do not call blocking ops when !TASK_RUNNING; state=2 set at [<ffffffff81098621>] prepare_to_wait+0x65/0xac
> > > [    3.553354] Modules linked in:
> > > [    3.554032] CPU: 3 PID: 1568 Comm: modprobe Not tainted 4.9.0-rc8-nofstest5-next-20161209-00013-g3134766e941a #1018
> > > [    3.556099] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-20161025_171302-gandalf 04/01/2014
> > > [    3.557330] Call Trace:
> > > [    3.557330]  dump_stack+0x68/0x92
> > > [    3.557330]  __warn+0xc2/0xdd
> > > [    3.557330]  warn_slowpath_fmt+0x4b/0x53
> > > [    3.557330]  ? prepare_to_wait+0x65/0xac
> > > [    3.557330]  ? prepare_to_wait+0x65/0xac
> > > [    3.557330]  __might_sleep+0x69/0x7e
> > > [    3.557330]  do_ide_request+0x47/0x540
> > > [    3.557330]  ? __lock_is_held+0x47/0x7a
> > > [    3.557330]  ? hrtimer_try_to_cancel+0x15f/0x1c6
> > > [    3.557330]  ? _raw_spin_unlock_irqrestore+0x4c/0x61
> > > [    3.557330]  __blk_run_queue+0x31/0x3a
> > > [    3.557330]  cfq_insert_request+0x331/0x429
> > > [    3.557330]  __elv_add_request+0x2bb/0x346
> > > [    3.557330]  blk_flush_plug_list+0x1da/0x21f
> > > [    3.557330]  ? bit_wait+0x50/0x50
> > > [    3.557330]  io_schedule_timeout+0x47/0x102
> > > [    3.557330]  bit_wait_io+0x1b/0x5a
> > > [    3.557330]  __wait_on_bit+0x4d/0x7b
> > > [    3.557330]  out_of_line_wait_on_bit+0x72/0x7d
> > > [    3.557330]  ? bit_wait+0x50/0x50
> > > [    3.557330]  ? autoremove_wake_function+0x4e/0x4e
> > > [    3.557330]  __wait_on_buffer+0x40/0x43
> > > [    3.557330]  bh_submit_read+0x60/0x72
> > > [    3.557330]  ext4_get_branch+0x91/0x115
> > > [    3.557330]  ext4_ind_map_blocks+0x181/0xa16
> > > [    3.557330]  ? __lock_is_held+0x47/0x7a
> > > [    3.557330]  ? lock_acquire+0x133/0x1c7
> > > [    3.557330]  ext4_map_blocks+0x120/0x4ca
> > > [    3.557330]  ext4_mpage_readpages+0x2a7/0x70a
> > > [    3.557330]  ext4_readpages+0x33/0x35
> > > [    3.557330]  __do_page_cache_readahead+0x239/0x32a
> > > [    3.557330]  filemap_fault+0x180/0x602
> > > [    3.557330]  ? filemap_fault+0x180/0x602
> > > [    3.557330]  ext4_filemap_fault+0x37/0x4b
> > > [    3.557330]  __do_fault+0x1f/0x94
> > > [    3.557330]  handle_mm_fault+0x946/0xfca
> > > [    3.557330]  __do_page_fault+0x361/0x518
> > > [    3.557330]  do_page_fault+0x42/0x5f
> > > [    3.557330]  page_fault+0x22/0x30
> > > 
> > > At first I thought this would be related to you recent work
> > > http://lkml.kernel.org/r/1477673892-28940-1-git-send-email-tj@kernel.org
> > > but that doesn't seem to be in the linux-next I am using as a base.
> > > io_schedule_timeout is on the stack though so you might have an idea
> > > what is going on here. That might_sleep check has been added a long ago
> > > 02e7cf8f8488 ("ide-cd,atapi: use bio for internal commands") in 2.6.31
> > > so I am wondering what has changed since than.
> > 
> > 10d784eae2b4 ("sched: always use blk_schedule_flush_plug in
> > io_schedule_out") seems related.  might_sleep is complaining that it's
> > being called while !TASK_RUNNING.  Shaohua, any ideas?
> 
> I can't see how the patch is related. Both blk_flush_plug and
> blk_schedule_flush_plug can sleep. The patch should only change
> behavior for plug which accepts from_schedule, which IIRC only raid
> code uses it.

Is there anything I could test?
-- 
Michal Hocko
SUSE Labs

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#1545959 — Re: WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738 __might_sleep+0x69/0x7e

FromCong Wang <xiyou.wangcong@gmail.com>
Date2016-12-21 20:30 +0100
SubjectRe: WARNING: CPU: 3 PID: 1568 at kernel/sched/core.c:7738 __might_sleep+0x69/0x7e
Message-ID<sQUKl-7uR-1@gated-at.bofh.it>
In reply to#1545714
On Wed, Dec 21, 2016 at 2:47 AM, Michal Hocko <mhocko@kernel.org> wrote:
>
> Is there anything I could test?

I am working on a patchset, will send them for you to test. Meanwhile,
if you could provide me a reproducer, that would help a lot.

Thanks!

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#1546001

FromMichal Hocko <mhocko@kernel.org>
Date2016-12-21 22:00 +0100
Message-ID<sQW9r-8fu-1@gated-at.bofh.it>
In reply to#1545959
On Wed 21-12-16 11:24:47, Cong Wang wrote:
> On Wed, Dec 21, 2016 at 2:47 AM, Michal Hocko <mhocko@kernel.org> wrote:
> >
> > Is there anything I could test?
> 
> I am working on a patchset, will send them for you to test. Meanwhile,
> if you could provide me a reproducer, that would help a lot.

I just boot my kvm image. Nothing really special here.
-- 
Michal Hocko
SUSE Labs

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