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From: Nishanth Aravamudan <nacc@us.ibm.com>
To: kernel-janitors@vger.kernel.org
Subject: Re: [KJ] thread_info.h use kzalloc
Date: Tue, 11 Jul 2006 17:05:16 +0000	[thread overview]
Message-ID: <20060711170516.GG4250@us.ibm.com> (raw)
In-Reply-To: <8ef77f2e0607110947j6fd6ec3fgb180f05ca8654eb8@mail.gmail.com>

On 11.07.2006 [18:47:14 +0200], tom hisch wrote:
> hello,
> 
> i have some questions about the alloc_thread_info(tsk) macro in
> asm-i386/thread_info.h
> 
> 
> /* thread information allocation */
> #ifdef CONFIG_DEBUG_STACK_USAGE
> #define alloc_thread_info(tsk)                                  \
>        ({                                                      \
>                struct thread_info *ret;                        \
>                                                                \
> ------>      ret = kmalloc(THREAD_SIZE, GFP_KERNEL);         \  //  what
> about the use of kzalloc ??
>                if (ret)                                        \
>                        memset(ret, 0, THREAD_SIZE);            \

Probably a reasonable change.

> ------>      ret;                                            \    // whats
> the meaning of this instruction ??
>        })

I think it's part of the magic of the ({ }) gcc'ism, which allows the
macro to effectively have a return value (that's how I think of it, at
least) without a return statement (in this case, the value of ret will
be stored in the corresponding lhs). I'm sure the real explanation can
be found in the gcc manual in the ({ }) section.

Thanks,
Nish

-- 
Nishanth Aravamudan <nacc@us.ibm.com>
IBM Linux Technology Center
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  reply	other threads:[~2006-07-11 17:05 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-07-11 16:47 [KJ] thread_info.h use kzalloc tom hisch
2006-07-11 17:05 ` Nishanth Aravamudan [this message]
2006-07-11 17:09 ` Alexey Dobriyan

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