Re: task_stat splat

[Oleg Nesterov]

On 11/23, Borislav Petkov wrote:
>
> where we end up with a zero PMD. RIP is corrupted too so we're somewhere
> off in the fields.

PMD = 0 is fine I guess, addr == 0 is not mapped.

> Comment over thread_group_cputime() talks about dead tasks accounting

This comment simply means that we also need to read the accumulated
counters in tsk->signal.

> which might be relevant as we're seeing not mapped page hierarchy so
> something must have gone away recently but we try to look at it.

This is called under ->siglock, we can't race with exit/etc. But this
doesn't matter, it is not that we (say) get t == NULL or something like
this.

RIP == 0, and this looks "impossible", I do not see indirect function
calls in this paths.

> [42460.389625] Call Trace:
> [42460.389635]  [<ffffffff810813d9>] ? task_sched_runtime+0x99/0xc0
> [42460.389643]  [<ffffffff81088b5c>] thread_group_cputime+0x17c/0x2d0

Could you identify somehow the line which matches task_sched_runtime+0x99 ?
Probably do_task_delta_exec()...

Oleg.

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