Messages in this thread | | | Subject | [linux-next-20130422] Bug in SLAB? | From | Tetsuo Handa <> | Date | Thu, 25 Apr 2013 21:20:47 +0900 |
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Tetsuo Handa wrote: > Hello. > > linux-next-20130422 does not boot when built with CONFIG_DEBUG_SLAB=y && > CONFIG_DEBUG_SPINLOCK=y && CONFIG_DEBUG_PAGEALLOC=y . > > It hangs (with CPU#0 spinning) immediately after printing > > Decompressing Linux... Parsing ELF... done. > Booting the kernel. > > lines. > > Config is at http://I-love.SAKURA.ne.jp/tmp/config-3.9-rc8-next-20130422 . > > Any clue before starting bisection? > > Regards. >
Bisection (with a build fix from commit db845067 "slab: Fixup CONFIG_PAGE_ALLOC/DEBUG_SLAB_LEAK sections") reached commit e3366016 "slab: Use common kmalloc_index/kmalloc_size functions". Would you have a look at commit e3366016?
By the way, I have a fear regarding commit e3366016.
include/linux/slab_def.h says
extern struct kmem_cache *kmalloc_caches[PAGE_SHIFT + MAX_ORDER]; extern struct kmem_cache *kmalloc_dma_caches[PAGE_SHIFT + MAX_ORDER];
while mm/slab.c says
struct kmem_cache *kmalloc_caches[KMALLOC_SHIFT_HIGH + 1]; struct kmem_cache *kmalloc_dma_caches[KMALLOC_SHIFT_HIGH + 1];
and include/linux/slab.h says
#define KMALLOC_SHIFT_HIGH ((MAX_ORDER + PAGE_SHIFT - 1) <= 25 ? \ (MAX_ORDER + PAGE_SHIFT - 1) : 25)
.
If (MAX_ORDER + PAGE_SHIFT - 1) <= 25 is true, mm/slab.c will allocate
struct kmem_cache *kmalloc_caches[MAX_ORDER + PAGE_SHIFT - 1 + 1]; struct kmem_cache *kmalloc_dma_caches[MAX_ORDER + PAGE_SHIFT - 1 + 1];
which matches the size declared in include/linux/slab_def.h .
If (MAX_ORDER + PAGE_SHIFT - 1) > 25 is true (I don't know whether such case happens), mm/slab.c will allocate
struct kmem_cache *kmalloc_caches[25 + 1]; struct kmem_cache *kmalloc_dma_caches[25 + 1];
which is smaller than the size declared in include/linux/slab_def.h .
Well, this mismatch seems to be fixed by commit 9425c58e "slab: Common definition for the array of kmalloc caches". But usage like
for (i = 1; i < PAGE_SHIFT + MAX_ORDER; i++) { struct kmem_cache_node *n; struct kmem_cache *cache = kmalloc_caches[i];
is remaining.
Also, kmalloc_index() in include/linux/slab.h can return 0 to 26.
If (MAX_ORDER + PAGE_SHIFT - 1) > 25 is true and kmalloc_index(64 * 1024 * 1024) is requested (I don't know whether such case happens), kmalloc_caches[26] is beyond the array, for kmalloc_caches[26] allows 0 to 25.
If (MAX_ORDER + PAGE_SHIFT - 1) <= 25 is true and kmalloc_index(64 * 1024 * 1024) is requested (I don't know whether such case happens), kmalloc_caches[26] is beyond the array, for kmalloc_caches[MAX_ORDER + PAGE_SHIFT] allows 0 to MAX_ORDER + PAGE_SHIFT - 1.
Would you recheck that the array size is correct?
Regards.
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