[PATCH] powerpc: on crash, kexec'ed kernel needs all CPUs are online

[Michael Ellerman]

On Thu, 2015-10-15 at 21:00 +0200, Laurent Vivier wrote:
> On kexec, all secondary offline CPUs are onlined before
> starting the new kernel, this is not done in the case of kdump.
> 
> If kdump is configured and a kernel crash occurs whereas
> some secondaries CPUs are offline (SMT=off),
> the new kernel is not able to start them and displays some
> "Processor X is stuck.".

Do we know why they are stuck?

I really don't like this fix. The reason we're doing a kdump is because the
first kernel has panicked, possibly with locks held or data structures
corrupted. Calling cpu_up() then goes and tries to run a bunch of code in the
crashed kernel, which increases the chance of us just wedging completely.

cheers