powerpc/smp: soft-replugged CPUs must go back to start_secondary

Various thing are torn down when a CPU is hot-unplugged. That CPU
is expected to go back to start_secondary when re-plugged to re
initialize everything, such as clock sources, maps, ...

Some implementations just return from cpu_die() callback
in the idle loop when the CPU is "re-plugged". This is not enough.

We fix it using a little asm trampoline which resets the stack
and calls back into start_secondary as if we were all fresh from
boot. The trampoline already existed on ppc64, but we add it for
ppc32

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index 66e237bbe15f..1de0e97a394f 100644
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -36,6 +36,7 @@ extern void cpu_die(void);
 
 extern void smp_send_debugger_break(int cpu);
 extern void smp_message_recv(int);
+extern void start_secondary_resume(void);
 
 DECLARE_PER_CPU(unsigned int, cpu_pvr);