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

[Kohli, Gaurav]

On 1/16/2018 12:50 PM, Alexey Dobriyan wrote:

> On Tue, Jan 16, 2018 at 11:06:47AM +0530, Kohli, Gaurav wrote:
> > On 1/10/2018 10:50 AM, Alexey Dobriyan 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:
> > > Please, post exact kernel version and struct task_struct::usage if you
> > > still have that kernel core (or even full task_struct)
> > Hi Alexey,
> >
> > We are working on 4.9.65 and Please find below usage value and other task_struct value,
> > please let me know if some other data required as well.
> Kernel stacks live their own lives nowadays, the code needs try_get_task_stack().
Hi Alexey,

Yes , agree we have to put some check like below

 if (permitted && (task->flags & PF_DUMPCORE) && try_get_task_stack(task)) {

ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ eip = KSTK_EIP(task);

ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ esp = KSTK_ESP(task);

ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ }

Or instead of this also , can't we check whether task is in exiting path or not by checking some flags like PF_EXITING.

Regards

Gaurav

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