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

John Garry
2017-06-14T13:08:16Z

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