[POWERPC] Fix smp_call_function to be preempt-safe

smp_call_function_map() was not safe against preemption to another
cpu: its test for removing self from map was outside the spinlock.
Rearrange it a little to fix that.

smp_call_function_single() was also wrong: now get_cpu() before
excluding self, as other architectures do.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 18 insertions, 16 deletions

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 22f1ef1b310..d577b71db37 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -201,13 +201,6 @@ int smp_call_function_map(void (*func) (void *info), void *info, int nonatomic,
         /* Can deadlock when called with interrupts disabled */
         WARN_ON(irqs_disabled());
 
-        /* remove 'self' from the map */
-        if (cpu_isset(smp_processor_id(), map))
-                cpu_clear(smp_processor_id(), map);
-
-        /* sanity check the map, remove any non-online processors. */
-        cpus_and(map, map, cpu_online_map);
-
         if (unlikely(smp_ops == NULL))
                 return ret;
 
@@ -222,10 +215,17 @@ int smp_call_function_map(void (*func) (void *info), void *info, int nonatomic,
         /* Must grab online cpu count with preempt disabled, otherwise
          * it can change. */
         num_cpus = num_online_cpus() - 1;
-        if (!num_cpus || cpus_empty(map)) {
-                ret = 0;
-                goto out;
-        }
+        if (!num_cpus)
+                goto done;
+
+        /* remove 'self' from the map */
+        if (cpu_isset(smp_processor_id(), map))
+                cpu_clear(smp_processor_id(), map);
+
+        /* sanity check the map, remove any non-online processors. */
+        cpus_and(map, map, cpu_online_map);
+        if (cpus_empty(map))
+                goto done;
 
         call_data = &data;
         smp_wmb();
@@ -263,6 +263,7 @@ int smp_call_function_map(void (*func) (void *info), void *info, int nonatomic,
                 }
         }
 
+ done:
         ret = 0;
 
  out:
@@ -282,16 +283,17 @@ EXPORT_SYMBOL(smp_call_function);
 int smp_call_function_single(int cpu, void (*func) (void *info), void *info, int nonatomic,
                         int wait)
 {
-        cpumask_t map=CPU_MASK_NONE;
+        cpumask_t map = CPU_MASK_NONE;
+        int ret = -EBUSY;
 
         if (!cpu_online(cpu))
                 return -EINVAL;
 
-        if (cpu == smp_processor_id())
-                return -EBUSY;
-
         cpu_set(cpu, map);
-        return smp_call_function_map(func,info,nonatomic,wait,map);
+        if (cpu != get_cpu())
+                ret = smp_call_function_map(func,info,nonatomic,wait,map);
+        put_cpu();
+        return ret;
 }
 EXPORT_SYMBOL(smp_call_function_single);