Date:	Tue, 6 Jan 2015 11:42:05 +0100
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	Dave Jones <davej@...emonkey.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: Re: Linux 3.19-rc3

On Tue, Jan 6, 2015 at 11:37 AM, Takashi Iwai <tiwai@...e.de> wrote:
> At Tue, 6 Jan 2015 11:31:34 +0100,
> Sedat Dilek wrote:
>>
>> On Tue, Jan 6, 2015 at 11:28 AM, Takashi Iwai <tiwai@...e.de> wrote:
>> > At Tue, 6 Jan 2015 11:06:45 +0100,
>> > Sedat Dilek wrote:
>> >>
>> >> On Tue, Jan 6, 2015 at 10:56 AM, Takashi Iwai <tiwai@...e.de> 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@...il.com> 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?
>> >
>> > Yes, it seems working for me at the last time I tried.
>> > (BTW, you don't need to add #include <linux/wait.h>)
>> >
>>
>> Just one minute ago, I asked about that?
>> Can you explain that - included by another include?
>
> Well, the original code calls the stuff defined in linux/wait.h, so
> it's already there obviously.
>

>From that POV you are right, but as said I checked parallelly
inotify_user.c which had this include.
Does it hurt to explicitly include again?

- Sedat -
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