Merge branch 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull smp fix from Thomas Gleixner:
 "Add warnings to the smp function calls so callers from wrong contexts
  get detected"

* 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  smp: Warn on function calls from softirq context

kernel/smp.c

@@ -291,6 +291,14 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
 	WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
 		     && !oops_in_progress);
 
+	/*
+	 * When @wait we can deadlock when we interrupt between llist_add() and
+	 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
+	 * csd_lock() on because the interrupt context uses the same csd
+	 * storage.
+	 */
+	WARN_ON_ONCE(!in_task());
+
 	csd = &csd_stack;
 	if (!wait) {
 		csd = this_cpu_ptr(&csd_data);
@@ -416,6 +424,14 @@ void smp_call_function_many(const struct cpumask *mask,
 	WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
 		     && !oops_in_progress && !early_boot_irqs_disabled);
 
+	/*
+	 * When @wait we can deadlock when we interrupt between llist_add() and
+	 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
+	 * csd_lock() on because the interrupt context uses the same csd
+	 * storage.
+	 */
+	WARN_ON_ONCE(!in_task());
+
 	/* Try to fastpath.  So, what's a CPU they want? Ignoring this one. */
 	cpu = cpumask_first_and(mask, cpu_online_mask);
 	if (cpu == this_cpu)