linux-kernel - Re: [PATCH v2 2/2] libsas: Enhance libsas hotplug

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Date:   Wed, 14 Jun 2017 17:15:43 +0800
From:   wangyijing <wangyijing@...wei.com>
To:     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>
Subject: Re: [PATCH v2 2/2] libsas: Enhance libsas hotplug

>> In this patch, we try to solve these issues in following steps:
>> 1. create a new workqueue used to run sas event work, instead of scsi host workqueue,
>>    because we may block sas event work, we cannot block the normal scsi works.
>>    When libsas receive a phy down event, sas_deform_port would be called, and now we
>>    block sas_deform_port and wait for destruction work finish, in sas_destruct_devices,
>>    we may wait ata error handler, it would take a long time, so if do all stuff in scsi
>>    host workq, libsas may block other scsi works too long.
>> 2. create a new workqueue used to run sas discovery events work, instead of scsi host
>>    workqueue, because in some cases, eg. in revalidate domain event, we may unregister
>>    a sas device and discover new one, we must sync the execution, wait the remove process
>>    finish, then start a new discovery. So we must put the probe and destruct discovery
>>    events in a new workqueue to avoid deadlock.
>> 3. introudce a asd_sas_port level wait-complete and a sas_discovery level wait-complete
>>    we use former wait-complete to achieve a sas event atomic process and use latter to
>>    make a sas discovery sync.
>> 4. remove disco_mutex in sas_revalidate_domain, since now sas_revalidate_domain sync
>>    the destruct discovery event execution, it's no need to lock disco mutex there.
> 
> The way you've written the changelog suggests this patch should be split
> into 4 patches, each one taking care of one of your change items.

I will split it in next version.

Thanks!
Yijing.


>