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

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On Fri, May 19, 2017 at 11:39 PM, Yijing Wang <wangyijing@huawei.com> 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
> new work[PORTE_BYTES_DMAED] --> |[PHYE_LOSS_OF_SIGNAL][PORTE_BYTES_DMAED] -> processing
>                                 |<-------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:

sas_port_event_fns
sas_phy_event_fns
sas_ha_event_fns

...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?

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[PATCH 1/2] libsas: Don't process sas events in static works Yijing Wang <wangyijing@huawei.com> - 2017-05-20 08:40 +0200
  Re: [PATCH 1/2] libsas: Don't process sas events in static works Dan Williams <dan.j.williams@intel.com> - 2017-05-21 05:50 +0200
    Re: [PATCH 1/2] libsas: Don't process sas events in static works wangyijing <wangyijing@huawei.com> - 2017-05-22 08:00 +0200
      Re: [PATCH 1/2] libsas: Don't process sas events in static works John Garry <john.garry@huawei.com> - 2017-05-22 11:30 +0200
        Re: [PATCH 1/2] libsas: Don't process sas events in static works wangyijing <wangyijing@huawei.com> - 2017-05-23 08:50 +0200

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