linux-kernel - Re: [patch 07/13] Initialize per cpu lowcores on cpu hotplug.

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Date:	Tue, 19 Feb 2008 19:44:42 +0100
From:	Segher Boessenkool <segher@...nel.crashing.org>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Bastian Blank <bastian@...di.eu.org>, linux-kernel@...r.kernel.org,
	linux-s390@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [patch 07/13] Initialize per cpu lowcores on cpu hotplug.

>>>> +	/*
>>>> +	 * Only need to copy the first 512 bytes from address 0. But since
>>>> +	 * the compiler emits a warning if src == NULL for memcpy use 
>>>> copy_page
>>>> +	 * instead. Copies more than needed but this code is not 
>>>> performance
>>>> +	 * critical.
>>>> +	 */
>>>> +	copy_page(lowcore, &S390_lowcore);
>>>
>>> Boah, workaround alert. Why do you not fix the compiler?
>>
>> We need to copy from address 0 (that's where the lowcore resides). 
>> But gcc
>> insists to complain if memcpy is used with src == NULL.. Now what?
>
> Erm sorry, misread your question. Usually it's a bug to use memcpy with
> src == NULL. In this case it's ok. So I think it's perfectly ok if gcc
> emits a warning.
> If you know of a better way to get around this please let me know.

-ffreestanding or -Wno-nonnull?


Segher

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