On Sat, 30 Nov 2013, Meelis Roos wrote: On Sat, 30 Nov 2013, Meelis Roos wrote: > I am debugging a reboot problem on Sun Ultra 5 (sparc64) with 512M RAM > and turned on DEBUG_PAGEALLOC DEBUG_SLAB and DEBUG_SLAB_LEAK (and most > other debug options) and got the following BUG and hang on startup. This > happened originally with 3.11-rc2-00058 where my bisection of > another problem lead, but I retested 3.12 to have the same BUG in the > same place. Hmmm. With CONFIG_DEBUG_PAGEALLOC *and* DEBUG_SLAB you would get a pretty strange configuration with massive sizes of slabs. > kernel BUG at mm/slab.c:2391! Ok so this means that we are trying to create a cache with off slab management during bootstrap which should not happen. > __kmem_cache_create: starting, size=248, flags=8192 > __kmem_cache_create: now flags=76800 > __kmem_cache_create: aligned size to 248 because of redzoning > __kmem_cache_create: pagealloc debug, setting size to 8192 > __kmem_cache_create: aligned size to 8192 > __kmem_cache_create: num=1, slab_size=64 > __kmem_cache_create: starting, size=96, flags=8192 > __kmem_cache_create: now flags=76800 > __kmem_cache_create: aligned size to 96 because of redzoning > __kmem_cache_create: pagealloc debug, setting size to 8192 > __kmem_cache_create: aligned size to 8192 > __kmem_cache_create: num=1, slab_size=64 > __kmem_cache_create: starting, size=192, flags=8192 > __kmem_cache_create: now flags=76800 > __kmem_cache_create: aligned size to 192 because of redzoning > __kmem_cache_create: pagealloc debug, setting size to 8192 > __kmem_cache_create: aligned size to 8192 > __kmem_cache_create: num=1, slab_size=64 > __kmem_cache_create: starting, size=32, flags=8192 > __kmem_cache_create: now flags=76800 > __kmem_cache_create: aligned size to 32 because of redzoning > __kmem_cache_create: aligned size to 32 > __kmem_cache_create: num=226, slab_size=960 > __kmem_cache_create: starting, size=64, flags=8192 > __kmem_cache_create: now flags=76800 > __kmem_cache_create: aligned size to 64 because of redzoning > __kmem_cache_create: pagealloc debug, setting size to 8192 > __kmem_cache_create: turning on CFLGS_OFF_SLAB, size=8192 We should not be switching on CFLGS_OFF_SLAB here because the kmalloc array does not contain the necessary entries yet. Does this fix it? We may need a more sophisticated fix from someone who knows how handle CONFIG_DEBUG_PAGEALLOC. Subject: slab: Do not use off slab metadata for CONFIG_DEBUG_PAGEALLOC Signed-off-by: Christoph Lameter <cl@xxxxxxxxx> Index: linux/mm/slab.c =================================================================== --- linux.orig/mm/slab.c 2013-12-03 09:44:20.463144282 -0600 +++ linux/mm/slab.c 2013-12-03 09:45:09.321786608 -0600 @@ -2243,13 +2243,15 @@ __kmem_cache_create (struct kmem_cache * * it too early on. Always use on-slab management when * SLAB_NOLEAKTRACE to avoid recursive calls into kmemleak) */ +#ifndef CONFIG_DEBUG_PAGEALLOC if ((size >= (PAGE_SIZE >> 3)) && !slab_early_init && - !(flags & SLAB_NOLEAKTRACE)) + !(flags & SLAB_NOLEAKTRACE) ) /* * Size is large, assume best to place the slab management obj * off-slab (should allow better packing of objs). */ flags |= CFLGS_OFF_SLAB; +#endif size = ALIGN(size, cachep->align); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>