linux-kernel - Re: Bad psi_group_cpu.tasks[NR

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Message-ID: <CAJuCfpFfLjqoP1ojkUU9uV_2QQ43CFXD-2fkjoZk=Sg8iWVkBA@mail.gmail.com>
Date: Mon, 12 Aug 2024 14:33:22 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Max Kellermann <max.kellermann@...os.com>
Cc: Johannes Weiner <hannes@...xchg.org>, Peter Zijlstra <peterz@...radead.org>, 
	linux-kernel@...r.kernel.org
Subject: Re: Bad psi_group_cpu.tasks[NR_MEMSTALL] counter

On Mon, Aug 12, 2024 at 1:06 AM Max Kellermann <max.kellermann@...os.com> wrote:
>
> On Tue, Aug 6, 2024 at 5:56 PM Suren Baghdasaryan <surenb@...gle.com> wrote:
> > Hmm. The original scenario I was thinking about when I proposed this
> > WARN_ON() was deemed impossible, so I think the only other possibility
> > is that the task being killed somehow skipped psi_memstall_leave()
> > before its death... Did you have the instrumentation I suggested to
> > track imbalance between psi_memstall_enter()/psi_memstall_leave() and
> > to record the _RET_IP_? If so, did it trigger at all?
>
> No, unfortunately I did not have the instrumentation because I don't
> know how this works (and didn't have the time to find out). If you
> have a patch for me, I can merge it into our kernel fork so we have
> the data next time it occurs.

Ok. Will you be able to enable CONFIG_DEBUG_INFO for this test to
symbolize reported _RET_IP_ once we capture it?

>
> Max