On Thu, Sep 02, 2010 at 03:46:00PM +0800, hutao@xxxxxxxxxxxxxx wrote:
> Hi,
>
> I got a problem where it seemed crash got a bad backtrace.
> The problem occurred under the following conditions:
> On a qemu guest system loading a module that stuck at
> the init function(say, call a function that did deadlooping),
> then dumped the guest by `virsh dump vm dumpfile', and run
> crash on the dumpfile.
>
> The module is:
>
> ---
> #include <linux/module.h>
>
> int endless_loop(void)
> {
> printk("endless loop\n");
> while (1);
>
> return 0;
> }
>
> int __init endless_init(void)
> {
> endless_loop();
>
> return 0;
> }
> module_init(endless_init);
>
> MODULE_LICENSE("GPL");
> ---
>
> crash bt command got:
>
> crash> bt -a
> PID: 0 TASK: ffffffff81648020 CPU: 0 COMMAND: "swapper"
> #0 [ffffffff81601e08] schedule at ffffffff813e8a49
> #1 [ffffffff81601e18] apic_timer_interrupt at ffffffff8100344e
> #2 [ffffffff81601ea0] need_resched at ffffffff8100970c
> #3 [ffffffff81601eb0] default_idle at ffffffff81009f6b
> #4 [ffffffff81601ec0] cpu_idle at ffffffff81001bf5
>
> PID: 1088 TASK: ffff88001dda2d60 CPU: 1 COMMAND: "insmod"
> #0 [ffff88001e751dc8] schedule at ffffffff813e8a49
> #1 [ffff88001e751dd0] schedule at ffffffff813e8aec
> #2 [ffff88001e751e80] preempt_schedule_irq at ffffffff813e8c90
> #3 [ffff88001e751e90] retint_kernel at ffffffff813eab86
> #4 [ffff88001e751f20] do_one_initcall at ffffffff81000210
> #5 [ffff88001e751f50] sys_init_module at ffffffff8106b7ca
> #6 [ffff88001e751f80] system_call_fastpath at ffffffff81002a82
> RIP: 00007f761bb58b7a RSP: 00007fff67a43120 RFLAGS: 00010206
> RAX: 00000000000000af RBX: ffffffff81002a82 RCX: 0000000000020010
> RDX: 0000000000b96010 RSI: 00000000000163da RDI: 0000000000b96030
> RBP: 0000000000b96010 R8: 0000000000010011 R9: 0000000000080000
> R10: 00007f761bb4b140 R11: 0000000000000202 R12: 00000000000163da
> R13: 00007fff67a44985 R14: 00000000000163da R15: 0000000000b96010
> ORIG_RAX: 00000000000000af CS: 0033 SS: 002b
>
> Does it lose some function calls between do_one_initcall and retint_kernel?
> (endless_loop <- endless_init)
>
In addition, if we don't stick in the init function (there is still a deadloop
somewhere in module but triggered by, say, reading a /proc file) then the backtrace
outputed by crash is correct.
>
> --
> Thanks,
> Hu Tao
>
> --
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--
Thanks,
Hu Tao
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