[LTP] [PATCH v3] Correctly check setitimer params in setitimer01

[Andrea Cervesato]

We use CLOCK_MONOTONIC_COARSE as our time resolution for checking
setitimer counter boundaries.

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
Margin in ITIMER_REAL is 0
Add some comments

 .../kernel/syscalls/setitimer/setitimer01.c   | 52 +++++++++++++------
 1 file changed, 35 insertions(+), 17 deletions(-)

diff --git a/testcases/kernel/syscalls/setitimer/setitimer01.c b/testcases/kernel/syscalls/setitimer/setitimer01.c
index eb62f02c6..e967577ed 100644
--- a/testcases/kernel/syscalls/setitimer/setitimer01.c
+++ b/testcases/kernel/syscalls/setitimer/setitimer01.c
@@ -8,7 +8,7 @@
 /*\
  * [Description]
  *
- * Spawn a child and verify that setitimer() syscall passes, and it ends up
+ * Spawn a child, verify that setitimer() syscall passes and it ends up
  * counting inside expected boundaries. Then verify from the parent that our
  * syscall sent the correct signal to the child.
  */
@@ -22,7 +22,8 @@
 #include "tst_safe_clocks.h"
 
 static struct itimerval *value, *ovalue;
-static unsigned long time_step;
+static long time_step;
+static long time_count;
 
 static struct tcase {
 	int which;
@@ -56,7 +57,7 @@ static void verify_setitimer(unsigned int i)
 {
 	pid_t pid;
 	int status;
-	int usec = 3 * time_step;
+	long margin;
 	struct tcase *tc = &tcases[i];
 
 	pid = SAFE_FORK();
@@ -66,7 +67,7 @@ static void verify_setitimer(unsigned int i)
 
 		tst_no_corefile(0);
 
-		set_setitimer_value(usec, 0);
+		set_setitimer_value(time_count, 0);
 		TST_EXP_PASS(sys_setitimer(tc->which, value, NULL));
 
 		set_setitimer_value(5 * time_step, 7 * time_step);
@@ -76,7 +77,14 @@ static void verify_setitimer(unsigned int i)
 			ovalue->it_value.tv_sec,
 			ovalue->it_value.tv_usec);
 
-		if (ovalue->it_value.tv_sec != 0 || ovalue->it_value.tv_usec > usec)
+		/*
+		 * ITIMER_VIRTUAL and ITIMER_PROF timers always expire a
+		 * time_step afterward the elapsed time to make sure that
+		 * at least counters take effect.
+		 */
+		margin = tc->which == ITIMER_REAL ? 0 : time_step;
+
+		if (ovalue->it_value.tv_sec != 0 || ovalue->it_value.tv_usec > time_count + margin)
 			tst_res(TFAIL, "Ending counters are out of range");
 
 		for (;;)
@@ -93,24 +101,34 @@ static void verify_setitimer(unsigned int i)
 
 static void setup(void)
 {
-	struct timespec res;
-
-	SAFE_CLOCK_GETRES(CLOCK_MONOTONIC, &res);
-
-	time_step = res.tv_nsec / 1000;
-	if (time_step < 10000)
-		time_step = 10000;
-
-	tst_res(TINFO, "clock resolution: %luns, time step: %luus",
-		res.tv_nsec,
-		time_step);
+	struct timespec time_res;
+
+	/*
+	 * We use CLOCK_MONOTONIC_COARSE resolution for all timers, since
+	 * we are sure its value is bigger than CLOCK_MONOTONIC and we can use
+	 * it for both realtime and virtual/prof timers resolutions.
+	 */
+	SAFE_CLOCK_GETRES(CLOCK_MONOTONIC_COARSE, &time_res);
+
+	time_step = time_res.tv_nsec / 1000;
+	if (time_step <= 0)
+		time_step = 1000;
+
+	time_count = 3 * time_step;
+
+	tst_res(TINFO, "clock resolution: %luns, "
+		"time step: %luus, "
+		"time count: %luus",
+		time_res.tv_nsec,
+		time_step,
+		time_count);
 }
 
 static struct tst_test test = {
 	.tcnt = ARRAY_SIZE(tcases),
 	.forks_child = 1,
-	.test = verify_setitimer,
 	.setup = setup,
+	.test = verify_setitimer,
 	.bufs = (struct tst_buffers[]) {
 		{&value,  .size = sizeof(struct itimerval)},
 		{&ovalue, .size = sizeof(struct itimerval)},
-- 
2.35.3