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

From: Dan Williams
Date: Sat May 20 2017 - 23:44:49 EST

On Fri, May 19, 2017 at 11:39 PM, Yijing Wang <wangyijing@xxxxxxxxxx> wrote:
> Now libsas hotplug work is static, LLDD driver queue
> the hotplug work into shost->work_q. If LLDD driver
> burst post lots hotplug events to libsas, the hotplug
> events may pending in the workqueue like
> shost->work_q
> |<-------wait worker to process-------->|
> In this case, a new PORTE_BYTES_DMAED event coming, libsas try to queue it
> to shost->work_q, but this work is already pending, so it would be lost.
> Finally, libsas delete the related sas port and sas devices, but LLDD driver
> expect libsas add the sas port and devices(last sas event).
> This patch remove the static defined hotplug work, and use dynamic work to
> avoid missing hotplug events.

If we go this route we don't even need:


...just specify the target routine directly to INIT_WORK() and remove
the indirection.

I also think for safety this should use a mempool that guarantees that
events can continue to be processed under system memory pressure.
Also, have you considered the case when a broken phy starts throwing a
constant stream of events? Is there a point at which libsas should
stop queuing events and disable the phy?