Re: Linux 3.19-rc3

[Sedat Dilek]

On Tue, Jan 6, 2015 at 10:56 AM, Takashi Iwai <tiwai@xxxxxxx> wrote:
> At Tue, 6 Jan 2015 10:34:30 +0100,
> Sedat Dilek wrote:
>>
>> On Tue, Jan 6, 2015 at 5:49 AM, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
>> > [ Please CC me I am not subscribed to LKML ]
>> >
>> > [ QUOTE ]
>> >
>> > On Mon, Jan 05, 2015 at 05:46:15PM -0800, Linus Torvalds wrote:
>> >  > It's a day delayed - not because of any particular development issues,
>> >  > but simply because I was tiling a bathroom yesterday. But rc3 is out
>> >  > there now, and things have stayed reasonably calm. I really hope that
>> >  > implies that 3.19 is looking good, but it's equally likely that it's
>> >  > just that people are still recovering from the holiday season.
>> >  >
>> >  > A bit over three quarters of the changes here are drivers - mostly
>> >  > networking, thermal, input layer, sound, power management. The rest is
>> >  > misc - filesystems, core networking, some arch fixes, etc. But all of
>> >  > it is pretty small.
>> >  >
>> >  > So go out and test,
>> >
>> > This has been there since just before rc1. Is there a fix for this
>> > stalled in someones git tree maybe ?
>> >
>> > [    7.952588] WARNING: CPU: 0 PID: 299 at kernel/sched/core.c:7303
>> > __might_sleep+0x8d/0xa0()
>> > [    7.952592] do not call blocking ops when !TASK_RUNNING; state=1
>> > set at [<ffffffff910a0f7a>] prepare_to_wait+0x2a/0x90
>> > [    7.952595] CPU: 0 PID: 299 Comm: systemd-readahe Not tainted
>> > 3.19.0-rc3+ #100
>> > [    7.952597]  0000000000001c87 00000000720a2c76 ffff8800b2513c88
>> > ffffffff915b47c7
>> > [    7.952598]  ffffffff910a3648 ffff8800b2513ce0 ffff8800b2513cc8
>> > ffffffff91062c30
>> > [    7.952599]  0000000000000000 ffffffff91796fb2 000000000000026d
>> > 0000000000000000
>> > [    7.952600] Call Trace:
>> > [    7.952603]  [<ffffffff915b47c7>] dump_stack+0x4c/0x65
>> > [    7.952604]  [<ffffffff910a3648>] ? down_trylock+0x28/0x40
>> > [    7.952606]  [<ffffffff91062c30>] warn_slowpath_common+0x80/0xc0
>> > [    7.952607]  [<ffffffff91062cc0>] warn_slowpath_fmt+0x50/0x70
>> > [    7.952608]  [<ffffffff910a0f7a>] ? prepare_to_wait+0x2a/0x90
>> > [    7.952610]  [<ffffffff910a0f7a>] ? prepare_to_wait+0x2a/0x90
>> > [    7.952611]  [<ffffffff910867ed>] __might_sleep+0x8d/0xa0
>> > [    7.952614]  [<ffffffff915b8ea9>] mutex_lock_nested+0x39/0x3e0
>> > [    7.952616]  [<ffffffff910a77ad>] ? trace_hardirqs_on+0xd/0x10
>> > [    7.952617]  [<ffffffff910a0fac>] ? prepare_to_wait+0x5c/0x90
>> > [    7.952620]  [<ffffffff911a63e0>] fanotify_read+0xe0/0x5b0
>> > [    7.952622]  [<ffffffff91090801>] ? sched_clock_cpu+0xc1/0xd0
>> > [    7.952624]  [<ffffffff91242459>] ? selinux_file_permission+0xb9/0x130
>> > [    7.952626]  [<ffffffff910a14d0>] ? prepare_to_wait_event+0xf0/0xf0
>> > [    7.952628]  [<ffffffff91162513>] __vfs_read+0x13/0x50
>> > [    7.952629]  [<ffffffff911625d8>] vfs_read+0x88/0x140
>> > [    7.952631]  [<ffffffff911626e7>] SyS_read+0x57/0xd0
>> > [    7.952633]  [<ffffffff915bd952>] system_call_fastpath+0x12/0x17
>> >
>> > [ /QUOTE ]
>> >
>> > I am seeing a similiar call-trace/warning.
>> > It is reproducible when running fio (latest: v2.2.4) while my loop-mq
>> > tests (see block.git#for-next)
>> >
>> > Some people tend to say it's coming from the linux-aio area [1], but I
>> > am not sure.
>> > 1st I thought this is a Linux-next problem but I am seeing it also
>> > with my rc-kernels.
>> > For parts of aio there is a patch discussed in [2].
>> > The experimental patchset of Ken from [3] made the "aio" call-trace go
>> > away here.
>> >
>> > I tried also a patch pending in peterz/queue.git#sched/core from Eric Sandeen.
>> > It's "check for stack overflow in ___might_sleep".
>> > Unfortunately, it did not help in case of my loop-mq tests.
>> > ( BTW, this is touching ___might_sleep() (note: triple-underscore VS.
>> > affected __might_sleep() <--- double-underscrore). )
>> >
>> > Let me hear your feedback.
>> >
>> > Have more fun!
>> >
>> > - Sedat -
>> >
>> > [1] http://marc.info/?l=linux-aio&m=142033318411355&w=2
>> > [2] http://marc.info/?l=linux-aio&m=142035799514685&w=2
>> > [3] http://evilpiepirate.org/git/linux-bcache.git/log/?h=aio_ring_fix
>> > [4] http://git.kernel.org/cgit/linux/kernel/git/peterz/queue.git/patch/?id=48e615e4c3ebed488fecb6bfb40b372151f62db2
>>
>> [ CC Takashi ]
>>
>> >From [1]:
>> ...
>>
>> Just "me too" (but overlooked until recently).
>>
>> The cause is a mutex_lock() call right after prepare_to_wait() with
>> TASK_INTERRUPTIBLE in fanotify_read().
>>
>> static ssize_t fanotify_read(struct file *file, char __user *buf,
>>     size_t count, loff_t *pos)
>> {
>> ....
>> while (1) {
>> prepare_to_wait(&group->notification_waitq, &wait, TASK_INTERRUPTIBLE);
>> mutex_lock(&group->notification_mutex);
>>
>> I saw Peter already fixed a similar code in inotify_user.c by commit
>> e23738a7300a (but interestingly for a different reason, "Deal with
>> nested sleeps").  Supposedly a similar fix would be needed for
>> fanotify_user.c.
>> ...
>>
>> Can you explain why do you think the problem is in sched-fanotify?
>>
>> I tried to do such a "similiar" (quick) fix analog to the mentioned
>> "sched, inotify: Deal with nested sleeps" patch from Peter.
>> If I did correct... It does not make the call-trace go away here.
>
> Your code path is different from what Dave and I hit.  Take a closer
> look at the stack trace.
>

Yeah, you are right.
I looked again into the code (see thread "Linux 3.19-rc3", I am
reading offline).

As said aio_ring_fix patchset and especially [1] fixed the issue for me.

Can you confirm Peter's new patch works-for-you?

- Sedat -

[0] http://marc.info/?t=142050755700004&r=1&w=2
[1] http://evilpiepirate.org/git/linux-bcache.git/commit/?h=aio_ring_fix&id=c91f0de111da37581709f7d201793a88c6993188
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