[Crash-utility] crash does not get proper backtrace?

[hutao at cn.fujitsu.com]

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)


-- 
Thanks,
Hu Tao