linux-kernel - Re: [PATCH v3 09/10] ntb_test: Add a selftest script for the NTB subsystem

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Date:	Wed, 15 Jun 2016 15:54:01 -0600
From:	Logan Gunthorpe <logang@...tatee.com>
To:	Allen Hubbe <Allen.Hubbe@....com>, 'Jon Mason' <jdmason@...zu.us>,
	'Dave Jiang' <dave.jiang@...el.com>
Cc:	'Shuah Khan' <shuahkh@....samsung.com>,
	'Sudip Mukherjee' <sudipm.mukherjee@...il.com>,
	'Arnd Bergmann' <arnd@...db.de>, linux-kernel@...r.kernel.org,
	linux-ntb@...glegroups.com, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v3 09/10] ntb_test: Add a selftest script for the NTB
 subsystem



On 15/06/16 03:49 PM, Allen Hubbe wrote:
>> +function link_test()
>> +{
>> +	LOC=$1
>> +	REM=$2
>> +	EXP=0
>> +
>> +	echo "Running link tests on: $(basename $LOC) / $(basename $REM)"
>> +
>> +	write_file "N" "$LOC/link"
>> +	write_file "N" "$LOC/link_event"
> 
> If it fails to bring down the link, won't it just block waiting on link_event and never make it to the next step of the test?
> 
>> +	if [[ $(read_file "$REM/link") != "N" ]]; then
>> +		echo "Expected remote link to be down in $REM/link" >&2
>> +		exit -1
>> +	fi
>> +
>> +	write_file "Y" "$LOC/link"
>> +	write_file "Y" "$LOC/link_event"
>> +
>> +	echo "  Passed"
>> +}

Well, the test is really intended to ensure both sides of the link see
changes to the link status. If the driver is somehow buggy and the link
never goes down/up when requested there's little I can do here except
block forever. Unless we want to add a timeout to the link_event file
(which I'd rather not).

You'd have the same issue if, when bringing the link up for the first
time, the link does not come back.

Logan