[LTP] [PATCH 1/2] ltp: Add the ability to specify the latency constraint

[Daniel Lezcano]

The ltp test suites provides a set of tests. Some of them are checking the test
happens in a specified amount of time.

Unfortunately, some platforms have slow power management routines adding more
than 1.5ms to wakeup from a deep idle state. This duration is far too long to
be acceptable when we are trying the measure a speficied routine with a timeout
reasonably delayed. For example, the testcases/kernel/syscalls/pselect_01 is
failing for this reason.

This patch gives the opportunity to the testcase to specify the latency
constraint when running. This option must be used with the needs_root in order
to have the right privileges.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 include/tst_test.h |  4 ++++
 lib/tst_test.c     | 18 ++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/include/tst_test.h b/include/tst_test.h
index e90312a..519fd4c 100644
--- a/include/tst_test.h
+++ b/include/tst_test.h
@@ -124,6 +124,7 @@ struct tst_test {
 	int needs_checkpoints:1;
 	int format_device:1;
 	int mount_device:1;
+	int needs_latency:1;
 
 	/* Minimal device size in megabytes */
 	unsigned int dev_min_size;
@@ -154,6 +155,9 @@ struct tst_test {
 
 	/* NULL terminated array of resource file names */
 	const char *const *resource_files;
+
+	/* Latency constraint to be set for the test */
+	int latency;
 };
 
 /*
diff --git a/lib/tst_test.c b/lib/tst_test.c
index 4c30eda..485515e 100644
--- a/lib/tst_test.c
+++ b/lib/tst_test.c
@@ -619,6 +619,21 @@ static void copy_resources(void)
 		TST_RESOURCE_COPY(NULL, tst_test->resource_files[i], NULL);
 }
 
+static int set_latency(void)
+{
+	int fd, ret;
+
+	fd = open("/dev/cpu_dma_latency", O_WRONLY);
+	if (fd < 0)
+		return fd;
+
+	ret = write(fd, &tst_test->latency, sizeof(tst_test->latency));
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
 static const char *get_tid(char *argv[])
 {
 	char *p;
@@ -736,6 +751,9 @@ static void do_setup(int argc, char *argv[])
 
 	if (tst_test->resource_files)
 		copy_resources();
+
+	if (tst_test->needs_latency && set_latency())
+		tst_brk(TCONF, "Failed to set cpu latency");
 }
 
 static void do_test_setup(void)
-- 
2.1.4