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

Pull perf fix from Ingo Molnar:
 "A single fix to not allow nonsensical event groups that result in
  kernel warnings"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/core: Fix group {cpu,task} validation

kernel/events/core.c

@@ -10032,28 +10032,27 @@ SYSCALL_DEFINE5(perf_event_open,
 			goto err_context;
 
 		/*
-		 * Do not allow to attach to a group in a different
-		 * task or CPU context:
+		 * Make sure we're both events for the same CPU;
+		 * grouping events for different CPUs is broken; since
+		 * you can never concurrently schedule them anyhow.
 		 */
-		if (move_group) {
+		if (group_leader->cpu != event->cpu)
+			goto err_context;
+
 		/*
 		 * Make sure we're both on the same task, or both
-			 * per-cpu events.
+		 * per-CPU events.
 		 */
 		if (group_leader->ctx->task != ctx->task)
 			goto err_context;
 
 		/*
-			 * Make sure we're both events for the same CPU;
-			 * grouping events for different CPUs is broken; since
-			 * you can never concurrently schedule them anyhow.
+		 * Do not allow to attach to a group in a different task
+		 * or CPU context. If we're moving SW events, we'll fix
+		 * this up later, so allow that.
 		 */
-			if (group_leader->cpu != event->cpu)
+		if (!move_group && group_leader->ctx != ctx)
 			goto err_context;
-		} else {
-			if (group_leader->ctx != ctx)
-				goto err_context;
-		}
 
 		/*
 		 * Only a group leader can be exclusive or pinned