smp: have smp_call_function_single() detect invalid CPUs

Have smp_call_function_single() return invalid CPU indicies and return
-ENXIO.  This function is already executed inside a
get_cpu()..put_cpu() which locks out CPU removal, so rather than
having the higher layers doing another layer of locking to guard
against unplugged CPUs do the test here.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/kernel/smp.c b/kernel/smp.c
index 782e2b93e465..f362a8553777 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -210,8 +210,10 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
 {
         struct call_single_data d;
         unsigned long flags;
-        /* prevent preemption and reschedule on another processor */
+        /* prevent preemption and reschedule on another processor,
+           as well as CPU removal */
         int me = get_cpu();
+        int err = 0;
 
         /* Can deadlock when called with interrupts disabled */
         WARN_ON(irqs_disabled());
@@ -220,7 +222,7 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
                 local_irq_save(flags);
                 func(info);
                 local_irq_restore(flags);
-        } else {
+        } else if ((unsigned)cpu < NR_CPUS && cpu_online(cpu)) {
                 struct call_single_data *data = NULL;
 
                 if (!wait) {
@@ -236,10 +238,12 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
                 data->func = func;
                 data->info = info;
                 generic_exec_single(cpu, data);
+        } else {
+                err = -ENXIO;   /* CPU not online */
         }
 
         put_cpu();
-        return 0;
+        return err;
 }
 EXPORT_SYMBOL(smp_call_function_single);