linux-kernel - Re: [PATCH 3/5] mm: Add kmalloc NULL tests

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Message-ID: <20090730191213.GA9471@cmpxchg.org>
Date:	Thu, 30 Jul 2009 21:12:14 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	Jörn Engel <joern@...fs.org>
Cc:	Julia Lawall <julia@...u.dk>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 3/5] mm: Add kmalloc NULL tests

On Thu, Jul 30, 2009 at 08:35:59PM +0200, Jörn Engel wrote:
> On Thu, 30 July 2009 17:36:58 +0200, Johannes Weiner wrote:
> > On Thu, Jul 30, 2009 at 04:10:22PM +0200, Julia Lawall wrote:
> > 
> > > diff --git a/mm/slab.c b/mm/slab.c
> > > index 7b5d4de..972e427 100644
> > > --- a/mm/slab.c
> > > +++ b/mm/slab.c
> > > @@ -1502,6 +1502,7 @@ void __init kmem_cache_init(void)
> > >  
> > >  		ptr = kmalloc(sizeof(struct arraycache_init), GFP_NOWAIT);
> > >  
> > > +		BUG_ON(!ptr);
> > >  		BUG_ON(cpu_cache_get(&cache_cache) != &initarray_cache.cache);
> > >  		memcpy(ptr, cpu_cache_get(&cache_cache),
> > >  		       sizeof(struct arraycache_init));
> > 
> > This does not change the end result when the allocation fails: you get
> > a stacktrace and a kernel panic.  Leaving it as is saves a line of
> > code.
> 
> According to http://lwn.net/Articles/342420/, there may be a subtle
> difference.

You will probably have a hard time establishing a userspace mapping
before slab is initializied :)
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