[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>

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 22f1ef1b3100ff8df55e8ab0f8256518b4c2987e..d577b71db37549433ca2f36aa6ad0bcea8cd3a5a 100644 (file)
--- 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);