linux-kernel - Re: initialization of static per-cpu variables

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Message-ID: <20080523142904.GB28257@cs181133002.pp.htv.fi>
Date:	Fri, 23 May 2008 17:29:04 +0300
From:	Adrian Bunk <bunk@...nel.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Vegard Nossum <vegard.nossum@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>
Subject: Re: initialization of static per-cpu variables

On Thu, May 22, 2008 at 06:20:06PM +1000, Rusty Russell wrote:
> On Thursday 22 May 2008 04:28:02 Vegard Nossum wrote:
> > Hi,
> >
> > I encountered this comment in kernel/softirq.c:
> >
> > /* Some compilers disobey section attribute on statics when not
> >    initialized -- RR */
> > static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec) = { NULL };
> > static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec) = { NULL };
> >
> > So I assume it's the combination of static and whatever section
> > DFINE_PER_CPU puts the variable in which is the problem.
> >
> > However, there's a LOT of these "static DEFINE_PER_CPU" without any
> > initializer in the rest of the code, e.g.:
> 
> Yep, it was an old toolchain used by Sparc: DaveM found this one.  As you say, 
> it's ancient: I'm happy to queue a cleanup patch now everyone is on a modern 
> compiler.

The commit says:

    [PATCH] softirq.c per_cpu fix
    
    GCC3.1 apparently gets confused about uninitialized sections


We do still support gcc 3.2 (which is the same as 3.1 except for a C++ 
ABI change) as a compiler for the kernel.


> Thanks,
> Rusty.

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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