linux-kernel - Re: [PATCH] [13/16] POISON: The high level memory error handler in the VM

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Message-ID: <20090407194034.GW17934@one.firstfloor.org>
Date:	Tue, 7 Apr 2009 21:40:34 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andi Kleen <andi@...stfloor.org>, hugh@...itas.com,
	npiggin@...e.de, riel@...hat.com, lee.schermerhorn@...com,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, x86@...nel.org
Subject: Re: [PATCH] [13/16] POISON: The high level memory error handler in the VM

On Tue, Apr 07, 2009 at 08:51:46PM +0200, Johannes Weiner wrote:
> > +
> > +	if (av == NULL)	/* Not actually mapped anymore */
> > +		goto out;
> > +
> > +	read_lock(&tasklist_lock);
> > +	for_each_process (tsk) {
> > +		if (!tsk->mm)
> > +			continue;
> > +		list_for_each_entry (vma, &av->head, anon_vma_node) {
> > +			if (vma->vm_mm == tsk->mm)
> > +				add_to_kill(tsk, page, vma, to_kill, tkc);
> > +		}
> > +	}
> > +	read_unlock(&tasklist_lock);
> > +out:
> > +	page_unlock_anon_vma(av);
> 
> If !av, this doesn't need an unlock and in fact crashes due to
> dereferencing NULL.

Good point. Fixed. Thanks.
> 
> > +static int poison_page_prepare(struct page *p, unsigned long pfn, int trapno)
> > +{
> > +	if (PagePoison(p)) {
> > +		printk(KERN_ERR
> > +		       "MCE: Error for already poisoned page at %lx\n", pfn);
> > +		return -1;
> > +	}
> > +	SetPagePoison(p);
> 
> TestSetPagePoison()?

It doesn't matter in this case because it doesn't need to be atomic.
The normal reason for TestSet is atomicity requirements. If someone
feels strongly about it I can add it.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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