linux-kernel - Re: [PATCH 13/25] scsi: hisi_sas: add path from phyup irq to SAS framework

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Date:	Mon, 19 Oct 2015 15:11:47 +0100
From:	John Garry <john.garry@...wei.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<James.Bottomley@...senpartnership.com>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linuxarm@...wei.com>, <zhangfei.gao@...aro.org>,
	<linux-scsi@...r.kernel.org>, <xuwei5@...ilicon.com>,
	<john.garry2@...l.dcu.ie>, <hare@...e.de>
Subject: Re: [PATCH 13/25] scsi: hisi_sas: add path from phyup irq to SAS
 framework

On 16/10/2015 14:36, Arnd Bergmann wrote:
> On Friday 16 October 2015 14:29:55 John Garry wrote:
>>
>> It could be considered.
>>
>> A potential issue I see is with hisi_sas_control_phy() for
>> PHY_FUNC_HARD_RESET: this allocates a hisi_sas_wq struct and processes
>> the reset in the queue work. When we re-enable the phy for the reset,
>> the phyup irq will want to use the same hisi_sas_wq struct which may be
>> in use.
>>
>> hisi_sas_control_phy() is added in 23/35.
>
> I'd have to review more closely, but I think that's fine, as this
> is how most work queues are used: you can queue the same function
> multiple times, and it's guaranteed to run at least once after
> the last queue, so if you queue it while it's already running,
> it will be called again, otherwise it won't.
>
> 	Arnd
>
> .
>
In the scenario I described the issue is not that the second call to 
queue the work function is lost. The problem is that when we setup the 
second call we may overwrite elements of the phy's hisi_sas_wq struct 
which may be still being referenced in the work function for the first call.

Regards,
John

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