linux-kernel - Re: [PATCH v3 10/10] ntb_perf: clear link_is

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Message-ID: <5761E0A0.4060505@deltatee.com>
Date:	Wed, 15 Jun 2016 17:11:28 -0600
From:	Logan Gunthorpe <logang@...tatee.com>
To:	"Jiang, Dave" <dave.jiang@...el.com>,
	"Allen.Hubbe@....com" <Allen.Hubbe@....com>,
	"jdmason@...zu.us" <jdmason@...zu.us>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"shuahkh@....samsung.com" <shuahkh@....samsung.com>,
	"sudipm.mukherjee@...il.com" <sudipm.mukherjee@...il.com>,
	"linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
	"arnd@...db.de" <arnd@...db.de>,
	"linux-ntb@...glegroups.com" <linux-ntb@...glegroups.com>
Subject: Re: [PATCH v3 10/10] ntb_perf: clear link_is_up flag when the link
 goes down.

Hey,

On 15/06/16 04:24 PM, Jiang, Dave wrote:
> On Wed, 2016-06-15 at 16:20 -0600, Logan Gunthorpe wrote:
>> Hey,
>>
>> Actually, I have to retract this patch. After some more thorough
>> testing
>> I'm finding an issue:
>>
>> When you remove and re-install the ntb_perf module very quickly,
>> ntb_perf will occasionally miss the link up event. This is because
>> the
>> link_cleanup work gets delayed long enough that it gets scheduled
>> after
>> the link up event gets sent. It then cancels the link work that
>> should
>> have occurred. Without this patch, it never happens because
>> link_is_up
>> never returns to false.
>>
>> I think the correct solution is to just remove the link_cleanup work
>> and
>> do those actions immediately on receipt of the event. If there's
>> agreement on this I can re-spin it again.
> 
> I'm ok with that. This is not an issue with ntb_transport?

Looks like I can get something similar to happen in ntb_transport.
However, it's much rarer and takes significantly more tries to get it to
occur. It does appear to correctly set its link_is_up to false when the
link goes down.

I'm not sure I'm quite clear on the flow in ntb_transport and don't have
time right now to study it so I'll have to let that be someone else's
(fairly minor) issue.

Logan