2 files changed, 30 insertions, 8 deletions

diff --git a/tools/tracing/rtla/src/timerlat_aa.c b/tools/tracing/rtla/src/timerlat_aa.c
index e0ffe69c271c..7093fd5333be 100644
--- a/tools/tracing/rtla/src/timerlat_aa.c
+++ b/tools/tracing/rtla/src/timerlat_aa.c
@@ -159,6 +159,7 @@ static int timerlat_aa_irq_latency(struct timerlat_aa_data *taa_data,
 	taa_data->thread_nmi_sum = 0;
 	taa_data->thread_irq_sum = 0;
 	taa_data->thread_softirq_sum = 0;
+	taa_data->thread_thread_sum = 0;
 	taa_data->thread_blocking_duration = 0;
 	taa_data->timer_irq_start_time = 0;
 	taa_data->timer_irq_duration = 0;
@@ -337,7 +338,23 @@ static int timerlat_aa_irq_handler(struct trace_seq *s, struct tep_record *recor
 		taa_data->timer_irq_start_time = start;
 		taa_data->timer_irq_duration = duration;
 
-		taa_data->timer_irq_start_delay = taa_data->timer_irq_start_time - expected_start;
+		/*
+		 * We are dealing with two different clock sources: the
+		 * external clock source that timerlat uses as a reference
+		 * and the clock used by the tracer. There are also two
+		 * moments: the time reading the clock and the timer in
+		 * which the event is placed in the buffer (the trace
+		 * event timestamp). If the processor is slow or there
+		 * is some hardware noise, the difference between the
+		 * timestamp and the external clock read can be longer
+		 * than the IRQ handler delay, resulting in a negative
+		 * time. If so, set IRQ start delay as 0. In the end,
+		 * it is less relevant than the noise.
+		 */
+		if (expected_start < taa_data->timer_irq_start_time)
+			taa_data->timer_irq_start_delay = taa_data->timer_irq_start_time - expected_start;
+		else
+			taa_data->timer_irq_start_delay = 0;
 
 		/*
 		 * not exit from idle.
@@ -528,7 +545,7 @@ static int timerlat_aa_kworker_start_handler(struct trace_seq *s, struct tep_rec
 static void timerlat_thread_analysis(struct timerlat_aa_data *taa_data, int cpu,
 				     int irq_thresh, int thread_thresh)
 {
-	unsigned long long exp_irq_ts;
+	long long exp_irq_ts;
 	int total;
 	int irq;
 
@@ -545,12 +562,15 @@ static void timerlat_thread_analysis(struct timerlat_aa_data *taa_data, int cpu,
 
 	/*
 	 * Expected IRQ arrival time using the trace clock as the base.
+	 *
+	 * TODO: Add a list of previous IRQ, and then run the list backwards.
 	 */
 	exp_irq_ts = taa_data->timer_irq_start_time - taa_data->timer_irq_start_delay;
-
-	if (exp_irq_ts < taa_data->prev_irq_timstamp + taa_data->prev_irq_duration)
-		printf("  Previous IRQ interference:	\t\t up to  %9.2f us\n",
-			ns_to_usf(taa_data->prev_irq_duration));
+	if (exp_irq_ts < taa_data->prev_irq_timstamp + taa_data->prev_irq_duration) {
+		if (taa_data->prev_irq_timstamp < taa_data->timer_irq_start_time)
+			printf("  Previous IRQ interference:	\t\t up to  %9.2f us\n",
+				ns_to_usf(taa_data->prev_irq_duration));
+	}
 
 	/*
 	 * The delay that the IRQ suffered before starting.
diff --git a/tools/tracing/rtla/src/timerlat_u.c b/tools/tracing/rtla/src/timerlat_u.c
index 05e310696dd5..01dbf9a6b5a5 100644
--- a/tools/tracing/rtla/src/timerlat_u.c
+++ b/tools/tracing/rtla/src/timerlat_u.c
@@ -45,7 +45,7 @@ static int timerlat_u_main(int cpu, struct timerlat_u_params *params)
 
 	retval = sched_setaffinity(gettid(), sizeof(set), &set);
 	if (retval == -1) {
-		err_msg("Error setting user thread affinity\n");
+		debug_msg("Error setting user thread affinity %d, is the CPU online?\n", cpu);
 		exit(1);
 	}
 
@@ -193,7 +193,9 @@ void *timerlat_u_dispatcher(void *data)
 					procs_count--;
 				}
 			}
-			break;
+
+			if (!procs_count)
+				break;
 		}
 
 		sleep(1);