powerpc: Update cpu_sibling_maps dynamically

Rather doing one initialization pass over all the per-cpu
cpu_sibling_maps at boot, update the maps at cpu online/offline time.

This is a behavior change -- the thread_siblings attribute now
reflects only online siblings, whereas it would display offline
siblings before.  The new behavior matches that of x86, and is
arguably more useful.

Signed-off-by: Nathan Lynch <ntl@pobox.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 29 insertions, 3 deletions

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index f5ae9fa222ea..3c4d07e5e06a 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -41,6 +41,7 @@
 #include <asm/smp.h>
 #include <asm/time.h>
 #include <asm/machdep.h>
+#include <asm/cputhreads.h>
 #include <asm/cputable.h>
 #include <asm/system.h>
 #include <asm/mpic.h>
@@ -228,6 +229,7 @@ void __devinit smp_prepare_boot_cpu(void)
         BUG_ON(smp_processor_id() != boot_cpuid);
 
         cpu_set(boot_cpuid, cpu_online_map);
+        cpu_set(boot_cpuid, per_cpu(cpu_sibling_map, boot_cpuid));
 #ifdef CONFIG_PPC64
         paca[boot_cpuid].__current = current;
 #endif
@@ -380,6 +382,7 @@ int __cpuinit __cpu_up(unsigned int cpu)
 int __devinit start_secondary(void *unused)
 {
         unsigned int cpu = smp_processor_id();
+        int i, base;
 
         atomic_inc(&init_mm.mm_count);
         current->active_mm = &init_mm;
@@ -400,6 +403,14 @@ int __devinit start_secondary(void *unused)
 
         ipi_call_lock();
         cpu_set(cpu, cpu_online_map);
+        /* Update sibling maps */
+        base = cpu_first_thread_in_core(cpu);
+        for (i = 0; i < threads_per_core; i++) {
+                if (cpu_is_offline(base + i))
+                        continue;
+                cpu_set(cpu, per_cpu(cpu_sibling_map, base + i));
+                cpu_set(base + i, per_cpu(cpu_sibling_map, cpu));
+        }
         ipi_call_unlock();
 
         local_irq_enable();
@@ -437,10 +448,25 @@ void __init smp_cpus_done(unsigned int max_cpus)
 #ifdef CONFIG_HOTPLUG_CPU
 int __cpu_disable(void)
 {
-        if (smp_ops->cpu_disable)
-                return smp_ops->cpu_disable();
+        int cpu = smp_processor_id();
+        int base, i;
+        int err;
 
-        return -ENOSYS;
+        if (!smp_ops->cpu_disable)
+                return -ENOSYS;
+
+        err = smp_ops->cpu_disable();
+        if (err)
+                return err;
+
+        /* Update sibling maps */
+        base = cpu_first_thread_in_core(cpu);
+        for (i = 0; i < threads_per_core; i++) {
+                cpu_clear(cpu, per_cpu(cpu_sibling_map, base + i));
+                cpu_clear(base + i, per_cpu(cpu_sibling_map, cpu));
+        }
+
+        return 0;
 }
 
 void __cpu_die(unsigned int cpu)