3.14-rc2 XFS backtrace because irqs_disabled.

[Oleg Nesterov]

On 02/14, Al Viro wrote:
>
> BTW, Oleg, could you explain why does PTRACE_PEEK_SIGINFO copy ->si_code
> separately?  IOW, why do we want the upper 16 bits of ->si_code exposed?
> It used to be a strictly internal thing IIRC (it's been what, 2.3.late?)

Yes, but checkpoint/restart tools want to dump/restore the internal part
of ->si_code too.

See also the "task_pid_vnr(current) == pid" hack in do_rt_sigqueueinfo(),
this allows to queue a SI_FROMKERNEL() siginfo.

Oleg.