kdump hangs up by Sysrq+C trigger in high load.

[Ingo Molnar]

* Yoshihiro Takahashi <ytakahashi at miraclelinux.com> wrote:

> Hi.
> 
> kdump hangs up by Sysrq+C trigger once in about 10 times in high load. 
> After the above occurs, kdump cannot collect vmcores with NMI button. 
> When waiting_for_crash_ipi does case more than 0, mdelay seem to make a 
> stall.
> 
> While nmi_shootdown_cpus(), mdelay may not work since interruption is 
> disable.  (ex. when crashing kernel by NMI interruption, all 
> interruption may be disabled.).
> 
> So I think that it should use other way (TSC) instead of mdelay() in 
> nmi_shootdown_cpus().

mdelay uses either the tsc or CPU loops - neither stop while IRQs are 
disabled.

Could you figure out exactly why it hangs in your case?

	Ingo