smp: Teach __smp_call_function_single() to check for offline cpus

Align __smp_call_function_single() with smp_call_function_single() so
that it also checks whether requested cpu is still online.
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

include/linux/smp.h

@@ -50,8 +50,7 @@ void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
 		smp_call_func_t func, void *info, bool wait,
 		gfp_t gfp_flags);
 
-void __smp_call_function_single(int cpuid, struct call_single_data *data,
-				int wait);
+int __smp_call_function_single(int cpu, struct call_single_data *csd, int wait);
 
 #ifdef CONFIG_SMP
 

kernel/smp.c

@@ -276,18 +276,18 @@ EXPORT_SYMBOL_GPL(smp_call_function_any);
 /**
  * __smp_call_function_single(): Run a function on a specific CPU
  * @cpu: The CPU to run on.
- * @data: Pre-allocated and setup data structure
+ * @csd: Pre-allocated and setup data structure
  * @wait: If true, wait until function has completed on specified CPU.
  *
  * Like smp_call_function_single(), but allow caller to pass in a
  * pre-allocated data structure. Useful for embedding @data inside
  * other structures, for instance.
  */
-void __smp_call_function_single(int cpu, struct call_single_data *csd,
-				int wait)
+int __smp_call_function_single(int cpu, struct call_single_data *csd, int wait)
 {
 	unsigned int this_cpu;
 	unsigned long flags;
+	int err = 0;
 
 	this_cpu = get_cpu();
 	/*
@@ -303,11 +303,14 @@ void __smp_call_function_single(int cpu, struct call_single_data *csd,
 		local_irq_save(flags);
 		csd->func(csd->info);
 		local_irq_restore(flags);
-	} else {
+	} else if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
 		csd_lock(csd);
 		generic_exec_single(cpu, csd, wait);
+	} else {
+		err = -ENXIO;	/* CPU not online */
 	}
 	put_cpu();
+	return err;
 }
 EXPORT_SYMBOL_GPL(__smp_call_function_single);
 

kernel/up.c

@@ -22,7 +22,7 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
 }
 EXPORT_SYMBOL(smp_call_function_single);
 
-void __smp_call_function_single(int cpu, struct call_single_data *csd,
+int __smp_call_function_single(int cpu, struct call_single_data *csd,
 			       int wait)
 {
 	unsigned long flags;
@@ -30,6 +30,7 @@ void __smp_call_function_single(int cpu, struct call_single_data *csd,
 	local_irq_save(flags);
 	csd->func(csd->info);
 	local_irq_restore(flags);
+	return 0;
 }
 EXPORT_SYMBOL(__smp_call_function_single);