ring-buffer: remove complex calculations in ring-buffer-test

Ingo Molnar thought that the code to calculate the time in cond_resched
is a bit too ugly and is not needed. This patch removes it and replaces
it with a simple call to cond_resched. I kept the comment that explains
the reason for the cond_resched.

[ Impact: remove ugly code ]
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

kernel/trace/ring_buffer_benchmark.c

@@ -185,35 +185,6 @@ static void ring_buffer_consumer(void)
 	complete(&read_done);
 }
 
-/*
- * If we are a non preempt kernel, the 10 second run will
- * stop everything while it runs. Instead, we will call cond_resched
- * and also add any time that was lost by a rescedule.
- */
-#ifdef CONFIG_PREEMPT
-static void sched_if_needed(struct timeval *start_tv, struct timeval *end_tv)
-{
-}
-#else
-static void sched_if_needed(struct timeval *start_tv, struct timeval *end_tv)
-{
-	struct timeval tv;
-
-	cond_resched();
-	do_gettimeofday(&tv);
-	if (tv.tv_usec < end_tv->tv_usec) {
-		tv.tv_usec += 1000000;
-		tv.tv_sec--;
-	}
-	start_tv->tv_sec += tv.tv_sec - end_tv->tv_sec;
-	start_tv->tv_usec += tv.tv_usec - end_tv->tv_usec;
-	if (start_tv->tv_usec > 1000000) {
-		start_tv->tv_usec -= 1000000;
-		start_tv->tv_sec++;
-	}
-}
-#endif
-
 static void ring_buffer_producer(void)
 {
 	struct timeval start_tv;
@@ -250,7 +221,13 @@ static void ring_buffer_producer(void)
 		if (consumer && !(++cnt % wakeup_interval))
 			wake_up_process(consumer);
 
-		sched_if_needed(&start_tv, &end_tv);
+		/*
+		 * If we are a non preempt kernel, the 10 second run will
+		 * stop everything while it runs. Instead, we will call
+		 * cond_resched and also add any time that was lost by a
+		 * rescedule.
+		 */
+		cond_resched();
 
 	} while (end_tv.tv_sec < (start_tv.tv_sec + RUN_TIME) && !kill_test);
 	pr_info("End ring buffer hammer\n");