linux-kernel - [PATCH 0/1] mm: fix the theoretical compound_lock() vs prep_new

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Message-ID: <20131219190846.GA24566@redhat.com>
Date:	Thu, 19 Dec 2013 20:08:46 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Jones <davej@...hat.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mgorman@...e.de>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: [PATCH 0/1] mm: fix the theoretical compound_lock() vs
	prep_new_page() race

On 12/16, Andrea Arcangeli wrote:
>
> Can you reorder set_page_refcount in your v2?

Please see the patch.

> I wonder if arch_alloc_page needs refcount 1, it sets the page as
> stable on s390.

Obviously I have no idea what set_page_stable() does, but it works
with page_to_phys(), unlikely the content of "struct page" can matter.
And only s390 HAVE_ARCH_ALLOC_PAGE, I added Martin and Heiko.

> the other way around is to move prep_compound_page
> before set_page_refcounted (though I think if we can, keeping the
> refcounted at the very last with a comment is preferable).

Yes, yes, this looks much more natural.

Oleg.

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