Commit b43a57bb authored Dec 06, 2006 by Kirill Korotaev Committed by Linus Torvalds Dec 07, 2006

[PATCH] OOM can panic due to processes stuck in __alloc_pages()



OOM can panic due to the processes stuck in __alloc_pages() doing infinite
rebalance loop while no memory can be reclaimed.  OOM killer tries to kill
some processes, but unfortunetaly, rebalance label was moved by someone
below the TIF_MEMDIE check, so buddy allocator doesn't see that process is
OOM-killed and it can simply fail the allocation :/

Observed in reality on RHEL4(2.6.9)+OpenVZ kernel when a user doing some
memory allocation tricks triggered OOM panic.

Signed-off-by: Denis Lunev <den@sw.ru>
Signed-off-by: Kirill Korotaev <dev@openvz.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent a3eea484

mm/page_alloc.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1180,6 +1180,7 @@ __alloc_pages(gfp_t gfp_mask, unsigned int order,

		/* This allocation should allow future memory freeing. */

		rebalance:
		if (((p->flags & PF_MEMALLOC) \|\| unlikely(test_thread_flag(TIF_MEMDIE)))
		&& !in_interrupt()) {
		if (!(gfp_mask & __GFP_NOMEMALLOC)) {
		@@ -1201,7 +1202,6 @@ __alloc_pages(gfp_t gfp_mask, unsigned int order,
		if (!wait)
		goto nopage;

		rebalance:
		cond_resched();

		/* We now go into synchronous reclaim */