Messages in this thread Patch in this message | | | Date | Wed, 5 Mar 2008 17:33:14 -0500 | From | Joe Korty <> | Subject | [PATCH] NUMA slab allocator migration bugfix |
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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>
Index: 2.6.25-rc4/mm/slab.c =================================================================== --- 2.6.25-rc4.orig/mm/slab.c 2008-03-05 16:07:56.000000000 -0500 +++ 2.6.25-rc4/mm/slab.c 2008-03-05 16:17:47.000000000 -0500 @@ -2964,11 +2964,10 @@ 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) { /*
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