[ARM] Fix SMP initialisation oops

A change to the SMP initialisation caused the following oops:

 CPU1: Booted secondary processor
 CPU1: D VIPT write-back cache
 CPU1: I cache: 32768 bytes, associativity 4, 32 byte lines, 256 sets
 CPU1: D cache: 32768 bytes, associativity 4, 32 byte lines, 256 sets
 <7>Calibrating delay loop... 83.14 BogoMIPS (lpj=415744)
 <1>Unable to handle kernel NULL pointer dereference at virtual address 0000001c
 ...
 PC is at enqueue_task+0x1c/0x64
 LR is at activate_task+0xcc/0xe4

SMP initialisation now requires cpu_possible_map to be initialised in
setup_arch().  Move this from smp_prepare_cpus() to smp_init_cpus()
and call it from our setup_arch() if CONFIG_SMP is enabled.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

4 files changed, 35 insertions, 13 deletions

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index c45d10d07bde..68273b4dc882 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -23,6 +23,7 @@
 #include <linux/root_dev.h>
 #include <linux/cpu.h>
 #include <linux/interrupt.h>
+#include <linux/smp.h>
 
 #include <asm/cpu.h>
 #include <asm/elf.h>
@@ -771,6 +772,10 @@ void __init setup_arch(char **cmdline_p)
         paging_init(&meminfo, mdesc);
         request_standard_resources(&meminfo, mdesc);
 
+#ifdef CONFIG_SMP
+        smp_init_cpus();
+#endif
+
         cpu_init();
 
         /*
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 7338948bd7d3..02aa300c4633 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -338,7 +338,6 @@ void __init smp_prepare_boot_cpu(void)
 
         per_cpu(cpu_data, cpu).idle = current;
 
-        cpu_set(cpu, cpu_possible_map);
         cpu_set(cpu, cpu_present_map);
         cpu_set(cpu, cpu_online_map);
 }
diff --git a/arch/arm/mach-integrator/platsmp.c b/arch/arm/mach-integrator/platsmp.c
index ea10bd8c972c..1bc8534ef0c6 100644
--- a/arch/arm/mach-integrator/platsmp.c
+++ b/arch/arm/mach-integrator/platsmp.c
@@ -140,6 +140,18 @@ static void __init poke_milo(void)
         mb();
 }
 
+/*
+ * Initialise the CPU possible map early - this describes the CPUs
+ * which may be present or become present in the system.
+ */
+void __init smp_init_cpus(void)
+{
+        unsigned int i, ncores = get_core_count();
+
+        for (i = 0; i < ncores; i++)
+                cpu_set(i, cpu_possible_map);
+}
+
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
         unsigned int ncores = get_core_count();
@@ -176,14 +188,11 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
                 max_cpus = ncores;
 
         /*
-         * Initialise the possible/present maps.
-         * cpu_possible_map describes the set of CPUs which may be present
-         * cpu_present_map describes the set of CPUs populated
+         * Initialise the present map, which describes the set of CPUs
+         * actually populated at the present time.
          */
-        for (i = 0; i < max_cpus; i++) {
-                cpu_set(i, cpu_possible_map);
+        for (i = 0; i < max_cpus; i++)
                 cpu_set(i, cpu_present_map);
-        }
 
         /*
          * Do we need any more CPUs? If so, then let them know where
diff --git a/arch/arm/mach-realview/platsmp.c b/arch/arm/mach-realview/platsmp.c
index a8fbd76d8be5..b8484e15dacb 100644
--- a/arch/arm/mach-realview/platsmp.c
+++ b/arch/arm/mach-realview/platsmp.c
@@ -143,6 +143,18 @@ static void __init poke_milo(void)
         mb();
 }
 
+/*
+ * Initialise the CPU possible map early - this describes the CPUs
+ * which may be present or become present in the system.
+ */
+void __init smp_init_cpus(void)
+{
+        unsigned int i, ncores = get_core_count();
+
+        for (i = 0; i < ncores; i++)
+                cpu_set(i, cpu_possible_map);
+}
+
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
         unsigned int ncores = get_core_count();
@@ -179,14 +191,11 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
         local_timer_setup(cpu);
 
         /*
-         * Initialise the possible/present maps.
-         * cpu_possible_map describes the set of CPUs which may be present
-         * cpu_present_map describes the set of CPUs populated
+         * Initialise the present map, which describes the set of CPUs
+         * actually populated at the present time.
          */
-        for (i = 0; i < max_cpus; i++) {
-                cpu_set(i, cpu_possible_map);
+        for (i = 0; i < max_cpus; i++)
                 cpu_set(i, cpu_present_map);
-        }
 
         /*
          * Do we need any more CPUs? If so, then let them know where