From 76bc11bd3c5eae50165c35edc17473e69e432fdf Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Fri, 18 Mar 2016 18:30:37 +0000
Subject: lib/igt_aux: Framework for measuring latency in raising signals

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 lib/igt_aux.c | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/igt_aux.h |  3 ++
 2 files changed, 98 insertions(+)

(limited to 'lib')

diff --git a/lib/igt_aux.c b/lib/igt_aux.c
index e64b29cc..d8e718f5 100644
--- a/lib/igt_aux.c
+++ b/lib/igt_aux.c
@@ -62,6 +62,7 @@
 #include "ioctl_wrappers.h"
 #include "igt_kms.h"
 #include "igt_pm.h"
+#include "igt_stats.h"
 
 /**
  * SECTION:igt_aux
@@ -1195,3 +1196,97 @@ void igt_set_module_param_int(const char *name, int val)
 
 	igt_set_module_param(name, str);
 }
+
+static struct igt_siglatency {
+	timer_t timer;
+	struct timespec target;
+	struct sigaction oldact;
+	struct igt_mean mean;
+
+	int sig;
+} igt_siglatency;
+
+static uint32_t
+__hars_petruska_f54_1_random (void)
+{
+	static uint32_t state = 0x12345678;
+
+#define rol(x,k) ((x << k) | (x >> (32-k)))
+	return state = (state ^ rol (state, 5) ^ rol (state, 24)) + 0x37798849;
+#undef rol
+}
+
+static long delay(void)
+{
+	return __hars_petruska_f54_1_random() % (NSEC_PER_SEC / 1000);
+}
+
+static double elapsed(const struct timespec *now, const struct timespec *last)
+{
+	double nsecs;
+
+	nsecs = now->tv_nsec - last ->tv_nsec;
+	nsecs += 1e9*(now->tv_sec - last->tv_sec);
+
+	return nsecs;
+}
+
+static void siglatency(int sig, siginfo_t *info, void *arg)
+{
+	struct itimerspec its;
+
+	clock_gettime(CLOCK_MONOTONIC, &its.it_value);
+	if (info)
+		igt_mean_add(&igt_siglatency.mean,
+			     elapsed(&its.it_value, &igt_siglatency.target));
+	igt_siglatency.target = its.it_value;
+
+	its.it_value.tv_nsec += 100 * 1000;
+	its.it_value.tv_nsec += delay();
+	if (its.it_value.tv_nsec >= NSEC_PER_SEC) {
+		its.it_value.tv_nsec -= NSEC_PER_SEC;
+		its.it_value.tv_sec += 1;
+	}
+	its.it_interval.tv_sec = its.it_interval.tv_nsec = 0;
+	timer_settime(igt_siglatency.timer, TIMER_ABSTIME, &its, NULL);
+}
+
+void igt_start_siglatency(int sig)
+{
+	struct sigevent sev;
+	struct sigaction act;
+
+	if (sig <= 0)
+		sig = SIGRTMIN;
+
+	if (igt_siglatency.sig)
+		(void)igt_stop_siglatency(NULL);
+	igt_assert(igt_siglatency.sig == 0);
+	igt_siglatency.sig = sig;
+
+	memset(&sev, 0, sizeof(sev));
+	sev.sigev_notify = SIGEV_SIGNAL | SIGEV_THREAD_ID;
+	sev.sigev_notify_thread_id = gettid();
+	sev.sigev_signo = sig;
+	timer_create(CLOCK_MONOTONIC, &sev, &igt_siglatency.timer);
+
+	memset(&act, 0, sizeof(act));
+	act.sa_sigaction = siglatency;
+	sigaction(sig, &act, &igt_siglatency.oldact);
+
+	siglatency(sig, NULL, NULL);
+}
+
+double igt_stop_siglatency(struct igt_mean *result)
+{
+	double mean = igt_mean_get(&igt_siglatency.mean);
+
+	if (result)
+		*result = igt_siglatency.mean;
+
+	sigaction(igt_siglatency.sig, &igt_siglatency.oldact, NULL);
+	timer_delete(igt_siglatency.timer);
+	memset(&igt_siglatency, 0, sizeof(igt_siglatency));
+
+	return mean;
+}
diff --git a/lib/igt_aux.h b/lib/igt_aux.h
index 30687423..be0d2d69 100644
--- a/lib/igt_aux.h
+++ b/lib/igt_aux.h
@@ -200,6 +200,9 @@ void igt_unlock_mem(void);
 	ret_;								\
 })
 
+struct igt_mean;
+void igt_start_siglatency(int sig); /* 0 => SIGRTMIN (default) */
+double igt_stop_siglatency(struct igt_mean *result);
 
 void igt_set_module_param(const char *name, const char *val);
 void igt_set_module_param_int(const char *name, int val);
-- 
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