Re: [ANNOUNCE] Support 'kdump' command from KDB in 2.6.27-rc2-*-2.bz2 patchset

On Thu, Aug 21, 2008 at 2:36 AM, Jay Lan <[email protected]> wrote:
> jidong xiao wrote:
>> On Sat, Aug 16, 2008 at 3:49 AM, Jay Lan <[email protected]> wrote:
>>> Hi,
>>>
>>> The kdb 2.6.27-rc2-*-2.bz2 patchset contains implementation
>>> of 'kdump' command. It was based on the original patch posted
>>> by Dan Aloni last year, then modified to provide i386 support
>>> by Jason Xiao. I added IA64 support. I also added hooks to
>>> intercept and drop to KDB from oops.
>>>
>>> It looks quite different from your patch, Jason, especially
>>> in kdb/kdbmain.c to a style i like better. Sorry about that.
>>>
>>> This implementation would catch die, panic, MCA, NMI conditions
>>> and drop into KDB. After analyze the oops situation and data,
>>> you can issue 'kdump' command and a kdump vmcore will be
>>> created.
>>>
>>> I do not intercept 'echo c > /proc/sysrq-trigger' since i see
>>> no need to create extra works if users already decide to create
>>> a vmcore from user space. Besides, you can use KDB key sequence
>>> to break into KDB and do a 'kdump' command to take a dump as well.
>>>
>>> Doing a 'go' after panic is undefined, and it also depends on
>>> the value of CONFIG_KDB_CONTINUE_CATASTROPHIC. So, do 'kdump'
>>> after panic if you want take a vmcore.
>>>
>>> I have tested on IA64 and X86_64 to see a kdump kernel booted
>>> up and /proc/vmcore created. Due to bugs of makedumpfile and
>>> crash against the latest kernels, i did not run crash to
>>> check validity of the vmcore though.
>>>
>>> Please report any bugs to me. Thanks!
>>>
>>> Regards,
>>>  - jay
>>>
>>>
>> Hi,Jay,
>>
>> arch/ia64/kdb/kdba_support.c,
>>
>> void
>> kdba_kdump_prepare(struct pt_regs *fixed_regs)
>> {
>>         int i;
>>
>>         /* Set on KEXEC bit on all onlinr cpus */
>>         for (i = 1; i < NR_CPUS; ++i) {
>>                 if (!cpu_online(i))
>>                         continue;
>>
>>                 KDB_STATE_SET_CPU(KEXEC, i);
>>         }
>>
>>         /* delaying for 5 seconds ... */
>>         udelay(5*1000000);
>>         machine_crash_shutdown(fixed_regs);
>> }
>>
>> I wonder why do we need this 5-seconds-delay. Thanks.
>
> I stole the code from ia64_init_handler() of arch/ia64/kernel/mca.c:
>
>        /*
>         * Wait for a bit.  On some machines (e.g., HP's zx2000 and
> zx6000, INIT can be
>         * generated via the BMC's command-line interface, but since the
> console is on the
>         * same serial line, the user will need some time to switch out
> of the BMC before
>         * the dump begins.
>         */
>        mprintk("Delaying for 5 seconds...\n");
>        udelay(5*1000000);
>        ia64_wait_for_slaves(cpu, "INIT");
>
> Since i can not test on those machines mentioned above, i can not tell
> if the delay is really necessary. But it is IA64 specific, i guess.
Okay, I see. Thanks.

>
> Have you tested the code on x86_32, Jason? I do not have an x86_32
> mchine set up for kdump testing...
>
I will test the code on x86_32 (and also ia64) soon. Will let you know
the result.

Regards
Jason

> Regards,
>  - jay
>
>>
>> Regards
>> Jason
>
>
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