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. > > kernel BUG at mm/slab.c:2391! > \|/ ____ \|/ > "@'/ .. \`@" > /_| \__/ |_\ > \__U_/ > swapper(0): Kernel bad sw trap 5 [#1] > CPU: 0 PID: 0 Comm: swapper Not tainted 3.11.0-rc2-00058-g20bafb3-dirty #127 > task: 00000000008ac468 ti: 000000000089c000 task.ti: 000000000089c000 > TSTATE: 0000004480e01606 TPC: 00000000004f57d4 TNPC: 00000000004f57d8 Y: 00000000 Not tainted > TPC: <__kmem_cache_create+0x374/0x480> > g0: 00000000000000f8 g1: 00000000008bb400 g2: 000000000002780b g3: 00000000008b5120 > g4: 00000000008ac468 g5: 0000000000000000 g6: 000000000089c000 g7: 0000000000000000 > o0: 0000000000845f08 o1: 0000000000000957 o2: ffffffffffffffe0 o3: 0000000000000000 > o4: 0000000000002004 o5: 0000000000000000 sp: 000000000089f301 ret_pc: 00000000004f57cc > RPC: <__kmem_cache_create+0x36c/0x480> > l0: fffff8001e812040 l1: fffff8001e819f80 l2: fffff8001e819fb8 l3: fffff8001e819fd8 > l4: 0000000000000001 l5: fffff8001e819fc8 l6: 0000000000845f08 l7: fffff8001e8300a0 > i0: fffff8001e831fa0 i1: 0000000080002800 i2: 0000000080000000 i3: 0000000000000034 > i4: 0000000000000000 i5: 0000000000002000 i6: 000000000089f3b1 i7: 0000000000907464 > I7: <create_boot_cache+0x4c/0x84> > Call Trace: > [0000000000907464] create_boot_cache+0x4c/0x84 > [00000000009074d0] create_kmalloc_cache+0x34/0x60 > [0000000000907540] create_kmalloc_caches+0x44/0x168 > [0000000000908dfc] kmem_cache_init+0x1d0/0x1e0 > [00000000008fc658] start_kernel+0x18c/0x370 > [0000000000761df4] tlb_fixup_done+0x88/0x94 > [0000000000000000] (null) > Disabling lock debugging due to kernel taint > Caller[0000000000907464]: create_boot_cache+0x4c/0x84 > Caller[00000000009074d0]: create_kmalloc_cache+0x34/0x60 > Caller[0000000000907540]: create_kmalloc_caches+0x44/0x168 > Caller[0000000000908dfc]: kmem_cache_init+0x1d0/0x1e0 > Caller[00000000008fc658]: start_kernel+0x18c/0x370 > Caller[0000000000761df4]: tlb_fixup_done+0x88/0x94 > Caller[0000000000000000]: (null) > Instruction DUMP: 92102957 7ffccb35 90122308 <91d02005> 90100018 4009b371 920f20d0 ba922000 02480006 > Kernel panic - not syncing: Attempted to kill the idle task! > Press Stop-A (L1-A) to return to the boot prom > > 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? 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? -- 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>