Re: [PATCH v2 1/2] libsas: Don't process sas events in static works

[John Garry]

On 14/06/2017 10:04, wangyijing wrote:
> > >  static void notify_ha_event(struct sas_ha_struct *sas_ha, enum ha_event event)
> > > >>  {
> > > >> +	struct sas_ha_event *ev;
> > > >> +
> > > >>  	BUG_ON(event >= HA_NUM_EVENTS);
> > > >>
> > > >> -	sas_queue_event(event, &sas_ha->pending,
> > > >> -			&sas_ha->ha_events[event].work, sas_ha);
> > > >> +	ev = kzalloc(sizeof(*ev), GFP_ATOMIC);
> > > >> +	if (!ev)
> > > >> +		return;
> > > GFP_ATOMIC allocations can fail and then no events will be queued *and* we
> > > don't report the error back to the caller.
> > >
> Yes, it's really a problem, but I don't find a better solution, do you have some suggestion ?

Dan raised an issue with this approach, regarding a malfunctioning PHY 
which spews out events. I still don't think we're handling it safely. 
Here's the suggestion:
- each asd_sas_phy owns a finite-sized pool of events
- when the event pool becomes exhausted, libsas stops queuing events 
(obviously) and disables the PHY in the LLDD
- upon attempting to re-enable the PHY from sysfs, libsas first checks 
that the pool is still not exhausted

If you cannot find a good solution, then let us know and we can help.

John