Re: 2.6.20-mm1 [kernel BUG at mm/swap.c:442]
From: James Morris
Date: Fri Feb 16 2007 - 09:30:48 EST
On Thu, 15 Feb 2007, Christoph Lameter wrote:
> On Thu, 15 Feb 2007, Andrew Morton wrote:
> > I don't immediately see why that code isn't racy: the page can remain
> > in the pagevec for arbitrary amounts of time and someone can come along
> > and mlock it again. But given the ease with which you're hitting this,
> > it may not be a race.
> As long as the page is on the pagevec it should be off the LRU.
> Marking a page PageMlocked requires the page to be on the LRU. So a page
> cannot be marked PageMlocked as long as it is on the regular pagevecs.
> Somehow a page off the LRU was marked PageMlocked. Or a new anonymous page
> was allocated and marked PageMlocked and then some later processing put it
> onto the LRU?
> Maybe try_to_set_mlocked does work some havoc here.
> Could you see if this patch fixes it? This just disabled an optimization
> to set PageMlocked early.
Nope, doesn't fix the problem.
> Index: linux-2.6.20-mm1/mm/memory.c
> --- linux-2.6.20-mm1.orig/mm/memory.c 2007-02-15 14:35:41.000000000 -0800
> +++ linux-2.6.20-mm1/mm/memory.c 2007-02-15 14:35:54.000000000 -0800
> @@ -930,6 +930,8 @@ static void try_to_set_mlocked(struct pa
> struct zone *zone;
> unsigned long flags;
> + return;
> if (!PageLRU(page) || PageMlocked(page))
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