perf: Simplify group_sched_in()

Collate the error paths. Code duplication only leads to divergence and
extra bugs.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201029162901.972161394@infradead.org

kernel/events/core.c

@@ -2580,11 +2580,8 @@ group_sched_in(struct perf_event *group_event,
 
 	pmu->start_txn(pmu, PERF_PMU_TXN_ADD);
 
-	if (event_sched_in(group_event, cpuctx, ctx)) {
-		pmu->cancel_txn(pmu);
-		perf_mux_hrtimer_restart(cpuctx);
-		return -EAGAIN;
-	}
+	if (event_sched_in(group_event, cpuctx, ctx))
+		goto error;
 
 	/*
 	 * Schedule in siblings as one group (if any):
@@ -2613,10 +2610,9 @@ group_error:
 	}
 	event_sched_out(group_event, cpuctx, ctx);
 
+error:
 	pmu->cancel_txn(pmu);
-
 	perf_mux_hrtimer_restart(cpuctx);
-
 	return -EAGAIN;
 }