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

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Message-ID: <CAKPOu+-8DXbCSj1OiWbS6+MuGPN9-kgsFkWn=hvr2cFwaDEEqA@mail.gmail.com>
Date: Mon, 12 Aug 2024 10:06:37 +0200
From: Max Kellermann <max.kellermann@...os.com>
To: Suren Baghdasaryan <surenb@...gle.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 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.

Max