linux-kernel - [PATCH] page-allocator: Ensure that processes that have been OOM killed exit the page allocator (resend)

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Message-ID: <20090715104944.GC9267@csn.ul.ie>
Date:	Wed, 15 Jul 2009 11:49:45 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	David Rientjes <rientjes@...gle.com>,
	Nick Piggin <npiggin@...e.de>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH] page-allocator: Ensure that processes that have been OOM
	killed exit the page allocator (resend)

Processes that have been OOM killed set the thread flag TIF_MEMDIE. A process
such as this is expected to exit the page allocator but potentially, it
loops forever. This patch checks TIF_MEMDIE when deciding whether to loop
again in the page allocator. If set, and __GFP_NOFAIL is not specified
then the loop will exit on the assumption it's no longer important for the
process to make forward progress. Note that a process that has just been
OOM-killed will still loop at least one more time retrying the allocation
before the thread flag is checked.

Signed-off-by: Mel Gorman <mel@....ul.ie>
--- 
 mm/page_alloc.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f8902e7..5c98d02 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1547,6 +1547,14 @@ should_alloc_retry(gfp_t gfp_mask, unsigned int order,
 	if (gfp_mask & __GFP_NORETRY)
 		return 0;
 
+	/* Do not loop if OOM-killed unless __GFP_NOFAIL is specified */
+	if (test_thread_flag(TIF_MEMDIE)) {
+		if (gfp_mask & __GFP_NOFAIL)
+			WARN(1, "Potential infinite loop with __GFP_NOFAIL");
+		else
+			return 0;
+	}
+
 	/*
 	 * In this implementation, order <= PAGE_ALLOC_COSTLY_ORDER
 	 * means __GFP_NOFAIL, but that may not be true in other
--
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