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>

diff --git a/kernel/smp.c b/kernel/smp.c
index 782e2b9..f362a85 100644 (file)
--- 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);