Re: [PATCH v3] psi: get poll_work to run when calling poll syscall next time

[Suren Baghdasaryan]

On Thu, Aug 22, 2019 at 3:21 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, 21 Aug 2019 11:26:25 +0800 Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx> wrote:
>
> > Only when calling the poll syscall the first time can user
> > receive POLLPRI correctly. After that, user always fails to
> > acquire the event signal.
> >
> > Reproduce case:
> > 1. Get the monitor code in Documentation/accounting/psi.txt
> > 2. Run it, and wait for the event triggered.
> > 3. Kill and restart the process.
> >
> > The question is why we can end up with poll_scheduled = 1 but the work
> > not running (which would reset it to 0). And the answer is because the
> > scheduling side sees group->poll_kworker under RCU protection and then
> > schedules it, but here we cancel the work and destroy the worker. The
> > cancel needs to pair with resetting the poll_scheduled flag.
>
> Should this be backported into -stable kernels?

Adding GregKH and stable@xxxxxxxxxxxxxxx

I was able to cleanly apply this patch to stable master and
linux-5.2.y branches (these are the only branches that have psi
triggers).
Greg, Andrew got this patch into -mm tree. Please advise on how we
should proceed to land it in stable 5.2.y and master.
Thanks,
Suren.