RE: [PATCH v2] acpi/ghes: Prevent sleeping with spinlock held

Dan Williams
2024-02-21T19:57:52Z

Ira Weiny wrote:
> Dan Williams wrote:
> > Ira Weiny wrote:
>
> [snip]
>
> > >
> > > - guard(rwsem_read)(&cxl_cper_rw_sem);
> > > - if (cper_callback)
> > > - cper_callback(event_type, rec);
> >
> > Given a work function can be set atomically there is no need to create /
> > manage a registration lock. Set a 'struct work' instance to a CXL
> > provided routine on cxl_pci module load and restore it to a nop function
> > + cancel_work_sync() on cxl_pci module exit.
>
> Ok I'll look into this.
>
> >
> > > + wi = kmalloc(sizeof(*wi), GFP_ATOMIC);
> >
> > The system is already under distress trying to report an error it should
> > not dip into emergency memory reserves to report errors. Use a kfifo()
> > similar to how memory_failure_queue() avoids memory allocation in the
> > error reporting path.
>
> I have a question on ghes_proc() [ghes_do_proc()]. Can they be called by
> 2 threads at the same time? It seems like there could be multiple
> platform devices which end up queueing into the single kfifo.

Yes, that is already the case for memory_failure_queue() and
aer_recover_queue().

> there needs to be a kfifo per device or synchronization with multiple
> writers.

Yes, follow the other _queue() examples. kfifo_in_spinlocked() looks
useful for this purpose.

I expect no lock needed on the read side since the reader is only the
single workqueue context.