[PATCH] powerpc: Don't start secondary CPUs in a UP && KEXEC kernel

[Michael Ellerman]

Because smp_release_cpus() is built for SMP || KEXEC, it's not safe to
unconditionally call it from setup_system(). On a UP && KEXEC kernel we'll
start up the secondary CPUs which will then go beserk and we die.

Simple fix is to conditionally call smp_release_cpus() in setup_system(). We
that in place we don't need the dummy definition of smp_release_cpus() because
all call sites are #ifdef'ed either SMP or KEXEC.

Signed-off-by: Michael Ellerman <michael at ellerman.id.au>
---

 arch/powerpc/kernel/setup_64.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

Index: kdump/arch/powerpc/kernel/setup_64.c
===================================================================
--- kdump.orig/arch/powerpc/kernel/setup_64.c
+++ kdump/arch/powerpc/kernel/setup_64.c
@@ -311,8 +311,6 @@ void smp_release_cpus(void)
 
 	DBG(" <- smp_release_cpus()\n");
 }
-#else
-#define smp_release_cpus()
 #endif /* CONFIG_SMP || CONFIG_KEXEC */
 
 /*
@@ -470,10 +468,12 @@ void __init setup_system(void)
 	check_smt_enabled();
 	smp_setup_cpu_maps();
 
+#ifdef CONFIG_SMP
 	/* Release secondary cpus out of their spinloops at 0x60 now that
 	 * we can map physical -> logical CPU ids
 	 */
 	smp_release_cpus();
+#endif
 
 	printk("Starting Linux PPC64 %s\n", system_utsname.version);