Re: psi_trigger_poll() is completely broken

[Linus Torvalds]

On Mon, Jan 10, 2022 at 9:25 AM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
>
> About the issue of serializing concurrent writes for
> cgroup_pressure_write() similar to how psi_write() does. Doesn't
> of->mutex inside kernfs_fop_write_iter() serialize the writes to the
> same file?

Ahh, yes, it looks like that does solve the serialization issue.
Sorry, I missed that because I'm not actually all that familiar with
the kernfs 'of' code.

So the only issue is the trigger lifetime one, and if a single trigger
is sufficient and returning -EBUSY for trying to replace an existing
one is good, then I think that's the proper fix.

I'm very busy with the merge window (and some upcoming travel and
family events), so I'm hoping somebody will write and test such a
patch. Please?

                   Linus