2013/12/3 Pekka Enberg <penberg@xxxxxx>: > On 11/30/2013 01:42 PM, 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. >> > > There was a rather large change to mm/slab.c that changed it to use 'struct > page' like SLUB. Perhaps slab debugging was broken in the process. Joonsoo, > does the problem Meelis describes ring a bell? Hello, Pekka. No. He report that BUG() is triggered on v3.11-rc2 and v3.12. And my recent change is merged into v3.13-rc1 as you know. :) Thanks. -- 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>