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>
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 9813605..1c9956c 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -502,7 +502,7 @@
}
/* Activate a secondary processor. */
-int __devinit start_secondary(void *unused)
+void __devinit start_secondary(void *unused)
{
unsigned int cpu = smp_processor_id();
struct device_node *l2_cache;
@@ -558,7 +558,8 @@
local_irq_enable();
cpu_idle();
- return 0;
+
+ BUG();
}
int setup_profiling_timer(unsigned int multiplier)
@@ -660,5 +661,9 @@
{
if (ppc_md.cpu_die)
ppc_md.cpu_die();
+
+ /* If we return, we re-enter start_secondary */
+ start_secondary_resume();
}
+
#endif