Merge tag 'smp-urgent-2020-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull SMP fixes from Thomas Gleixner:
 "Two fixes for the SMP related functionality:

   - Make the UP version of smp_call_function_single() match SMP
     semantics when called for a not available CPU. Instead of emitting
     a warning and assuming that the function call target is CPU0,
     return a proper error code like the SMP version does.

   - Remove a superfluous check in smp_call_function_many_cond()"

* tag 'smp-urgent-2020-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  smp/up: Make smp_call_function_single() match SMP semantics
  smp: Remove superfluous cond_func check in smp_call_function_many_cond()

Author: torvalds

kernel/smp.c

@@ -435,7 +435,7 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
 
 	/* Fastpath: do that cpu by itself. */
 	if (next_cpu >= nr_cpu_ids) {
-		if (!cond_func || (cond_func && cond_func(cpu, info)))
+		if (!cond_func || cond_func(cpu, info))
 			smp_call_function_single(cpu, func, info, wait);
 		return;
 	}

kernel/up.c

@@ -14,7 +14,8 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
 {
 	unsigned long flags;
 
-	WARN_ON(cpu != 0);
+	if (cpu != 0)
+		return -ENXIO;
 
 	local_irq_save(flags);
 	func(info);