Re: Query: Crash is coming during /prod/PID/stat and do_exit of same task

[Kohli, Gaurav]

On 1/15/2018 4:32 PM, John Ogness wrote:

> Hello Gaurav.
>
> On 2018-01-09, Kohli, Gaurav <gkohli@xxxxxxxxxxxxxx> wrote:
> > We are seeing crash in do_task_stat while accessing stack pointer, It
> > seems same task has already completed do_exit call.
> > So it seems a race between them:
> >
> > Below is the crash trace:
> > 49750.534377] Kernel BUG at ffffff8e7a4c53a8 [verbose debug info
> > unavailable]
> > [49750.534394] task: ffffffe7b4475580 task.stack: ffffffe7a5f0c000
> > [49750.534400] PC is at do_task_stat+0x740/0x908
> > [49750.534402] LR is at do_task_stat+0xa4/0x908
> > [49750.534403] pc : [<ffffff8e7a4c53a8>] lr : [<ffffff8e7a4c4d0c>]
> > pstate: 80400145
> > [49750.534404] sp : ffffffe7a5f0fbd0
> >
> > and here is stack trace on that core:
> >
> > -000|user_stack_pointer(inline)
> > -000|do_task_stat(
> >  ÂÂÂ |ÂÂÂ m = 0xFFFFFFE7A5CD7380,
> >  ÂÂÂ |ÂÂÂ ns = 0xFFFFFF8E7C43C748,
> >  ÂÂÂ |Â ?,
> >  ÂÂÂ |ÂÂÂ task = 0xFFFFFFE80D8C2280,
> >  ÂÂÂ |Â ?)
> >  ÂÂÂ |Â tty_pgrp = 0
> >  ÂÂÂ |Â ppid = 2084696064
> >  ÂÂÂ |Â sid = 0
> >  ÂÂÂ |Â mm = 0xFFFFFFE7B4424140
> >  ÂÂÂ |Â tcomm = (84, 9, 71, 122, 142, 255, 255, 255, 48, 253, 240, 165,
> > 231, 255, 255, 255)
> >  ÂÂÂ |Â flags = 18446743969119403392
> > -001|proc_tgid_stat(
> >  ÂÂÂ |ÂÂÂ m = 0xFFFFFFE7A5CD7380,
> >  ÂÂÂ |Â ?,
> >
> > Below are task stats which shows , process completed the do_exit call:
> > struct task_struct.flags -x 0xFFFFFFE80D8C2280
> >  Â flags = 0x40870c
> >
> > crash_64> struct task_struct.exit_code -x 0xFFFFFFE80D8C2280
> >  Â exit_code = 0x6
> >
> >  ÂÂ struct task_struct.state -x 0xFFFFFFE80D8C2280
> >  Â state = 0x40
> I am confused why this task is in the TASK_PARKED state. What kind of
> task is this?

Hi John,

This is android HAL layer service and also before bug, i am seeing lot of service exited in logs also,
although not seeing for this pid 6807

.452202:ÂÂ <2> init: starting service 'limits-hal-1-0'...

Â49749.460039:ÂÂ <2> init: property_set("ro.boottime.limits-hal-1-0", "61591320967789") failed: property already set

Â49749.607496:ÂÂ <6> sh (2422): drop_caches: 3

Â49750.281635:ÂÂ <6> sh (2422): drop_caches: 3

Â49750.533853:ÂÂ <2> init: Untracked pid 6811 exited with status 0

And why it is parked , that is not clear as state is already updated of task.

Regards

Gaurav

> > In our build both patches are there ,
> > fs/proc: report eip/esp in /prod/PID/stat for coredumping
> >
> > and also task.state has already set PF_DUMPCORE as it got the sigabrt
> > signal.
> John Ogness
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