[PATCH] powernv: Avoid calling trace tlbie in kexec path.

[Balbir Singh]

On Thu, Nov 23, 2017 at 4:32 AM, Mahesh J Salgaonkar
<mahesh at linux.vnet.ibm.com> wrote:
> From: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
>
> Rebooting into a new kernel with kexec fails in trace_tlbie() which is
> called from native_hpte_clear(). This happens if the running kernel has
> CONFIG_LOCKDEP enabled. With lockdep enabled, the tracepoints always
> execute few RCU checks regardless of whether tracing is on or off.
> We are already in the last phase of kexec sequence in real mode with
> HILE_BE set. At this point the RCU check ends up in RCU_LOCKDEP_WARN and
> causes kexec to fail.
>

Effectively we can't enter the trace point code after we've set
HILE_BE.  Do we need
a fixes tag? Or is this a side-effect of a new generic change?

I think the right thing in the longer run might be to do a TRACE_EVENT_CONDITION
and have the condition do the right thing, but what you have for now is good.

Balbir Singh.