Messages in this thread | | | Date | Thu, 10 Jul 2008 21:49:03 +0200 | From | "Vegard Nossum" <> | Subject | Re: v2.6.26-rc9: kernel BUG at kernel/sched.c:5858! |
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Okay, some more info on this one...
On Thu, Jul 10, 2008 at 4:16 PM, Vegard Nossum <vegard.nossum@gmail.com> wrote: > BUG: unable to handle kernel paging request at da87d000 > IP: [<c01991c7>] kmem_cache_alloc+0xc7/0xe0 > *pde = 28180163 *pte = 1a87d160 > Oops: 0002 [#1] PREEMPT SMP DEBUG_PAGEALLOC > Pid: 3850, comm: grep Not tainted (2.6.26-rc9-00059-gb190333 #5) > EIP: 0060:[<c01991c7>] EFLAGS: 00210203 CPU: 0 > EIP is at kmem_cache_alloc+0xc7/0xe0 > EAX: 00000000 EBX: da87c100 ECX: 1adad71a EDX: 6b6b6b6b > ESI: 00200282 EDI: da87d000 EBP: f60bfe74 ESP: f60bfe54 > DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
The register %ecx looks innocent but is very important here. The disassembly:
mov %edx,%ecx shr $0x2,%ecx rep stos %eax,%es:(%edi) <-- the fault
So %ecx has been loaded from %edx... which is 0x6b6b6b6b/POISON_FREE. (0x6b6b6b6b >> 2 == 0x1adadada.)
%ecx is the counter for the memset, from here:
memset(object, 0, c->objsize);
i.e. %ecx was loaded from c->objsize, so "c" must have been freed. Where did "c" come from? Uh-oh...
c = get_cpu_slab(s, smp_processor_id());
This looks like it has very much to do with CPU hotplug/unplug. Is there a race between SLUB/hotplug since the CPU slab is used after it has been freed?
Vegard
-- "The animistic metaphor of the bug that maliciously sneaked in while the programmer was not looking is intellectually dishonest as it disguises that the error is the programmer's own creation." -- E. W. Dijkstra, EWD1036
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