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

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Message-ID: <59423956.6070905@huawei.com>
Date:   Thu, 15 Jun 2017 15:37:58 +0800
From:   wangyijing <wangyijing@...wei.com>
To:     John Garry <john.garry@...wei.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        <jejb@...ux.vnet.ibm.com>, <martin.petersen@...cle.com>
CC:     <chenqilin2@...wei.com>, <hare@...e.com>,
        <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <chenxiang66@...ilicon.com>, <huangdaode@...ilicon.com>,
        <wangkefeng.wang@...wei.com>, <zhaohongjiang@...wei.com>,
        <dingtianhong@...wei.com>, <guohanjun@...wei.com>,
        <yanaijie@...wei.com>, <hch@....de>, <dan.j.williams@...el.com>,
        <emilne@...hat.com>, <thenzl@...hat.com>, <wefu@...hat.com>,
        <charles.chenxin@...wei.com>, <chenweilong@...wei.com>,
        Yousong He <heyousong@...wei.com>
Subject: Re: [PATCH v2 1/2] libsas: Don't process sas events in static works



在 2017/6/14 21:08, John Garry 写道:
> 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.

Hi John and Dan, what's event you found on malfunctioning PHY, if the event is PORTE_BROADCAST_RCVD, since
every PORTE_BROADCAST_RCVD libsas always call sas_revalidate_domain(), what about keeping a broadcast waiting(not queued in workqueue)
and discard others. If the event is other types, things may become knotty.


> 
> John
> 
> 
> .
>