From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <524E83D4.8070007@siemens.com>
Date: Fri, 04 Oct 2013 11:01:08 +0200
From: Jan Kiszka <jan.kiszka@siemens.com>
MIME-Version: 1.0
References: <1380568915-32582-1-git-send-email-gilles.chanteperdrix@xenomai.org>
	<524E7D5B.5080004@siemens.com>
	<fb449ebaab2d4e71a032af35d5a881b6.squirrel@127.0.0.1>
In-Reply-To: <fb449ebaab2d4e71a032af35d5a881b6.squirrel@127.0.0.1>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Subject: Re: [Xenomai] [PATCH] x86/ipipe: get FPU backup area allocated for
	all threads
List-Id: Discussions about the Xenomai project <xenomai.xenomai.org>
List-Unsubscribe: <http://www.xenomai.org/mailman/options/xenomai>,
	<mailto:xenomai-request@xenomai.org?subject=unsubscribe>
List-Archive: <http://www.xenomai.org/pipermail/xenomai>
List-Post: <mailto:xenomai@xenomai.org>
List-Help: <mailto:xenomai-request@xenomai.org?subject=help>
List-Subscribe: <http://www.xenomai.org/mailman/listinfo/xenomai>,
	<mailto:xenomai-request@xenomai.org?subject=subscribe>
To: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Cc: xenomai@xenomai.org

On 2013-10-04 10:53, Gilles Chanteperdrix wrote:
> 
> Jan Kiszka wrote:
>>> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
>>> index a00bed1..4716eb2 100644
>>> --- a/arch/x86/kernel/process.c
>>> +++ b/arch/x86/kernel/process.c
>>> @@ -73,14 +73,6 @@ int arch_dup_task_struct(struct task_struct *dst,
>>> struct task_struct *src)
>>>  		if (ret)
>>>  			return ret;
>>>  		fpu_copy(dst, src);
>>> -	} else {
>>> -#ifdef CONFIG_IPIPE
>>> -		/* unconditionally allocate, RT domain may need it */
>>> -		memset(&dst->thread.fpu, 0, sizeof(dst->thread.fpu));
>>> -		ret = fpu_alloc(&dst->thread.fpu);
>>> -		if (ret)
>>> -			return ret;
>>> -#endif
>>
>> Why removing the systematic allocation? This is not explained above and
>> seems counterproductive.
> 
> Because when we stop deleting the fpu backup area upon exec, no fork ever
> takes place for source thread without an fpu backup area. So, the "else"
> clause never happens, and we can remove it entirely.

OK, please add this to the commit log.

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux