[Crash-utility] [PATCH] Fix x86 initialization for {hard, soft}irq_ctx

[OGAWA Hirofumi]

Dave Anderson <anderson at redhat.com> writes:

>> >> crash> bt
>> >> PID: 0      TASK: c1da8b00  CPU: 0   COMMAND: "swapper/0"
>> >>  #0 [c1da1f60] __schedule at c19fe305
>> >>  #1 [c1da1fa0] schedule at c19febb3
>> >>  #2 [c1da1fac] schedule_preempt_disabled at c19ff0a2
>> >>  #3 [c1da1fb4] cpu_startup_entry at c10a9580
>> >> crash> bt 45
>> >> PID: 45     TASK: f57d3a00  CPU: 3   COMMAND: "kworker/3:1"
>> >> bt: cannot resolve stack trace:
>> >> bt: Task in user space -- no backtrace
>> >> 
>> >> In above case, looks like failed to detect panic cpu, and "bt 45" also
>> >> not working.
>> 
>> crash> bt 45
>> PID: 45     TASK: f57d3a00  CPU: 3   COMMAND: "kworker/3:1"
>> bt: cannot resolve stack trace:
>> bt: Task in user space -- no backtrace

Debugged this case. The root cause is nested stack of softirq =>
hardirq. Now doesn't handle it correctly, and the patch attacked.

BTW, with this patch, "bt -t" seems to be working at least. "bt" is
failed sometime by confusion of stack-frame detection, this one is
harder to fix.

[BTW, current x86_get_pc() uses inactive_task_frame_ret_addr to get
pc. However, inactive_task_frame is only valid if task is sleeping
state. (running task may overwrite inactive_task_frame already.)  I'm
not sure whether we should check is_task_active() or not. Even if
checking is_task_active(), we can't get pc correctly anyway.]

Thanks.
-- 
OGAWA Hirofumi <hirofumi at mail.parknet.co.jp>

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