linux-kernel - Re: [PATCH] mm, hugetlb: gimme back my page

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Message-ID: <1391190643.3475.7.camel@buesod1.americas.hpqcorp.net>
Date:	Fri, 31 Jan 2014 09:50:43 -0800
From:	Davidlohr Bueso <davidlohr@...com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Jonathan Gonzalez <jgonzalez@...ets.cl>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm, hugetlb: gimme back my page

On Thu, 2014-01-30 at 12:58 -0800, David Rientjes wrote:
> On Thu, 30 Jan 2014, Sasha Levin wrote:
> 
> > VM_BUG_ON_PAGE is just a VM_BUG_ON that does dump_page before the BUG().
> > 
> > The only reason to use VM_BUG_ON instead of VM_BUG_ON_PAGE is if the page
> > you're working
> > with doesn't make sense/isn't useful as debug output.
> > 
> > If doing a dump_page is causing issues somewhere then dump_pages should be
> > fixed - instead
> > of hiding the problem under the rug by not using it.
> > 
> 
> It sounds like dump_page() isn't necessarily at fault itself but rather 
> that using it is opening a race even wider that causes this failure to 
> occur more often than it normally would.

It turns out this issue goes way back, you just have try hard enough to
trigger it under very specific conditions.

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