> > 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. > > > > kernel BUG at mm/slab.c:2391! [... > > The line shows that __kmem_cache_create gets a NULL from kmalloc_slab(). > > > > I instrumented the code and found the following: > > > > __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 > > __kmem_cache_create: aligned size to 8192 > > __kmem_cache_create: num=1, slab_size=64 > > __kmem_cache_create: CFLGS_OFF_SLAB, size=8192, slab_size=52 > > __kmem_cache_create: CFLGS_OFF_SLAB, allocating slab 52 > > > > With slab size 64, it turns on CFLGS_OFF_SLAB and off slab allocation > > with this size fails. I do not know slab internals so I can not tell if > > this just happens because of the debug paths, or is it a real problem > > without the debug options too. > > > > Sounds like a problem with create_kmalloc_caches(), what are the values > for KMALLOC_SHIFT_LOW and KMALLOC_SHIFT_HIGH? KMALLOC_SHIFT_LOW=5, KMALLOC_SHIFT_HIGH=23 > It's interesting you report this as starting with 3.11-rc2 because this > changed in 3.9, what kernels were tested before 3.11-rc2 if any? No other kernels were tested with slab debug - but all relsese kernels and most rc-s starting with rc2 or rc3 eacg time were tested without slab debug. -- Meelis Roos (mroos@xxxxxxxx) -- 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>