Commit 6d2144d3 authored Mar 05, 2008 by Joe Korty Committed by Christoph Lameter Mar 06, 2008

slab: NUMA slab allocator migration bugfix



NUMA slab allocator cpu migration bugfix

The NUMA slab allocator (specifically, cache_alloc_refill)
is not refreshing its local copies of what cpu and what
numa node it is on, when it drops and reacquires the irq
block that it inherited from its caller.  As a result
those values become invalid if an attempt to migrate the
process to another numa node occured while the irq block
had been dropped.

The solution is to make cache_alloc_refill reload these
variables whenever it drops and reacquires the irq block.

The error is very difficult to hit.  When it does occur,
one gets the following oops + stack traceback bits in
check_spinlock_acquired:

	kernel BUG at mm/slab.c:2417
	cache_alloc_refill+0xe6
	kmem_cache_alloc+0xd0
	...

This patch was developed against 2.6.23, ported to and
compiled-tested only against 2.6.25-rc4.

Signed-off-by: Joe Korty <joe.korty@ccur.com>
Signed-off-by: Christoph Lameter <clameter@sgi.com>

parent b6210386

mm/slab.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -2964,11 +2964,10 @@ static void cache_alloc_refill(struct kmem_cache cachep, gfp_t flags)
		struct array_cache *ac;
		int node;

		node = numa_node_id();

		retry:
		check_irq_off();
		node = numa_node_id();
		ac = cpu_cache_get(cachep);
		retry:
		batchcount = ac->batchcount;
		if (!ac->touched && batchcount > BATCHREFILL_LIMIT) {
		/*