linux-kernel - Re: [PATCH 1/5] selftests: Add futex functional tests

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Message-ID: <555234ED.2000300@osg.samsung.com>
Date:	Tue, 12 May 2015 11:14:21 -0600
From:	Shuah Khan <shuahkh@....samsung.com>
To:	Darren Hart <dvhart@...radead.org>
CC:	Darren Hart <dvhart@...ux.intel.com>,
	Cyril Hrubis <chrubis@...e.cz>, linux-api@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	John Stultz <john.stultz@...aro.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Davidlohr Bueso <dave@...olabs.net>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [PATCH 1/5] selftests: Add futex functional tests

On 05/12/2015 11:05 AM, Darren Hart wrote:
> On Tue, May 12, 2015 at 10:47:14AM -0600, Shuah Khan wrote:
>> On 05/12/2015 10:10 AM, Darren Hart wrote:
>>> On 5/12/15, 3:02 AM, "Cyril Hrubis" <chrubis@...e.cz> wrote:
>>>
>>>> Hi!
>>>>> I'm happy to do that, but I would like to make sure I'm doing the right
>>>>> thing.
>>>>
>>>> The right thing here is to add -pthread to CFLAGS which sets both flags
>>>> for preprocessor and linker (see man gcc).
>>>
>>> Hi Cyril,
>>>
>>> Thanks. I read that, and mentioned it, but my concern with -pthread in the
>>> CFLAGS and LDFLAGS is that it is a non-standard compiler flag. I
>>> understand we have a number of gcc-isms in our build - but do we want to
>>> add more?
>>>
>>> I'm also struggling to find any kind of prescribed documentation on this
>>> beyond the short blurb in the gcc man page which describes what this
>>> option does, but not when to use it. I'll need something concrete to
>>> justify changes to testcase Makefiles to Shuah.
>>>
>>> Unfortunately, all these options are functional for me, while some are not
>>> for Shuah, so I'm currently having to rely on documentation which seems
>>> pretty sparse.
>>>
>>
>> Hi Daren,
>>
>> My goals are really simple. make kselftest doesn't break. All tests
>> compile and run and install or fail gracefully when dependencies aren't
>> met. As long as the above are met, I don't really worry about what
>> individual test Makefiles do.
> 
> Understood. Given the variability across distros/compiler versions, the
> "doesn't break" part isn't as straight forward as it should be. I could fix
> this so it builds for you and me, but I'm trying to build confidence that I'm
> doing this "correctly" so it doesn't break in other scenarios - since I'm not
> seeing any breakage on my systems.
> 
> Shuah, which distro and compiler version are you seeing the build failure on?
> I'd like to at least reproduce that so I can be confident my next version will
> at least build in your environment.
> 
> Currently, the only direction I have is gcc man page and Cyril's advocacy for
> -pthread. Does the following work for you (it still does for me)?
> 
> 
>>>From 0b7284551d6419520d5ce8833e177ba5b8be2286 Mon Sep 17 00:00:00 2001
> Message-Id: <0b7284551d6419520d5ce8833e177ba5b8be2286.1431449782.git.dvhart@...ux.intel.com>
> From: Darren Hart <dvhart@...ux.intel.com>
> Date: Tue, 12 May 2015 09:54:39 -0700
> Subject: [PATCH] selftests/futex: Add -pthread to CFLAGS and LDFLAGS
> 
> Certain environments fail to build with the "-lpthread -lrt" LDFLAGS.
> Using "-pthread" instead of "-lpthread" resolves this and is the
> documented mechanism in the gcc man page.
> 
> Signed-off-by: Darren Hart <dvhart@...ux.intel.com>
> ---
>  tools/testing/selftests/futex/functional/Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/futex/functional/Makefile b/tools/testing/selftests/futex/functional/Makefile
> index e64d43b..9d6b75e 100644
> --- a/tools/testing/selftests/futex/functional/Makefile
> +++ b/tools/testing/selftests/futex/functional/Makefile
> @@ -1,6 +1,6 @@
>  INCLUDES := -I../include -I../../
> -CFLAGS := $(CFLAGS) -g -O2 -Wall -D_GNU_SOURCE $(INCLUDES)
> -LDFLAGS := $(LDFLAGS) -lpthread -lrt
> +CFLAGS := $(CFLAGS) -g -O2 -Wall -D_GNU_SOURCE -pthread $(INCLUDES)
> +LDFLAGS := $(LDFLAGS) -pthread -lrt
>  
>  HEADERS := ../include/futextest.h
>  TARGETS := \
> 


Daren,

The above worked on my system. I have gcc version 4.9.2 (Ubuntu
4.9.2-10ubuntu13) on mine just in case you need that info.

thanks,
-- Shuah

-- 
Shuah Khan
Sr. Linux Kernel Developer
Open Source Innovation Group
Samsung Research America (Silicon Valley)
shuahkh@....samsung.com | (970) 217-8978
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