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Subject[PATCH 2/2] selftests: futex: Expand timeout test
Date
Improve futex timeout testing by checking all the operations that
supports timeout and their available modes.

Signed-off-by: André Almeida <andrealmeid@collabora.com>
---
.../futex/functional/futex_wait_timeout.c | 126 +++++++++++++++---
1 file changed, 110 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/futex/functional/futex_wait_timeout.c b/tools/testing/selftests/futex/functional/futex_wait_timeout.c
index ee55e6d389a3..1f8f6daaf1e7 100644
--- a/tools/testing/selftests/futex/functional/futex_wait_timeout.c
+++ b/tools/testing/selftests/futex/functional/futex_wait_timeout.c
@@ -11,21 +11,18 @@
*
* HISTORY
* 2009-Nov-6: Initial version by Darren Hart <dvhart@linux.intel.com>
+ * 2021-Apr-26: More test cases by André Almeida <andrealmeid@collabora.com>
*
*****************************************************************************/

-#include <errno.h>
-#include <getopt.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <time.h>
+#include <pthread.h>
#include "futextest.h"
#include "logging.h"

#define TEST_NAME "futex-wait-timeout"

static long timeout_ns = 100000; /* 100us default timeout */
+static futex_t futex_pi;

void usage(char *prog)
{
@@ -37,11 +34,67 @@ void usage(char *prog)
VQUIET, VCRITICAL, VINFO);
}

+/*
+ * Get a PI lock and hold it forever, so the main thread lock_pi will block
+ * and we can test the timeout
+ */
+void *get_pi_lock(void *arg)
+{
+ int ret;
+ volatile futex_t lock = 0;
+
+ ret = futex_lock_pi(&futex_pi, NULL, 0, 0);
+ if (ret != 0)
+ error("futex_lock_pi failed\n", ret);
+
+ /* Blocks forever */
+ ret = futex_wait(&lock, 0, NULL, 0);
+ error("futex_wait failed\n", ret);
+
+ return NULL;
+}
+
+/*
+ * Check if the function returned the expected error
+ */
+static void test_timeout(int res, int *ret, char *test_name, int err)
+{
+ if (!res || errno != err) {
+ ksft_test_result_fail("%s returned %d\n", test_name,
+ res < 0 ? errno : res);
+ *ret = RET_FAIL;
+ } else {
+ ksft_test_result_pass("%s succeeds\n", test_name);
+ }
+}
+
+/*
+ * Calculate absolute timeout and correct overflow
+ */
+static int futex_get_abs_timeout(clockid_t clockid, struct timespec *to,
+ long timeout_ns)
+{
+ if (clock_gettime(clockid, to)) {
+ error("clock_gettime failed\n", errno);
+ return errno;
+ }
+
+ to->tv_nsec += timeout_ns;
+
+ if (to->tv_nsec >= 1000000000) {
+ to->tv_sec++;
+ to->tv_nsec -= 1000000000;
+ }
+
+ return 0;
+}
+
int main(int argc, char *argv[])
{
futex_t f1 = FUTEX_INITIALIZER;
- struct timespec to;
int res, ret = RET_PASS;
+ struct timespec to;
+ pthread_t thread;
int c;

while ((c = getopt(argc, argv, "cht:v:")) != -1) {
@@ -65,22 +118,63 @@ int main(int argc, char *argv[])
}

ksft_print_header();
- ksft_set_plan(1);
+ ksft_set_plan(7);
ksft_print_msg("%s: Block on a futex and wait for timeout\n",
basename(argv[0]));
ksft_print_msg("\tArguments: timeout=%ldns\n", timeout_ns);

- /* initialize timeout */
+ pthread_create(&thread, NULL, get_pi_lock, NULL);
+
+ /* initialize relative timeout */
to.tv_sec = 0;
to.tv_nsec = timeout_ns;

- info("Calling futex_wait on f1: %u @ %p\n", f1, &f1);
- res = futex_wait(&f1, f1, &to, FUTEX_PRIVATE_FLAG);
- if (!res || errno != ETIMEDOUT) {
- fail("futex_wait returned %d\n", ret < 0 ? errno : ret);
- ret = RET_FAIL;
- }
+ res = futex_wait(&f1, f1, &to, 0);
+ test_timeout(res, &ret, "futex_wait relative", ETIMEDOUT);
+
+ /* FUTEX_WAIT_BITSET with CLOCK_REALTIME */
+ if (futex_get_abs_timeout(CLOCK_REALTIME, &to, timeout_ns))
+ return RET_FAIL;
+ res = futex_wait_bitset(&f1, f1, &to, 1, FUTEX_CLOCK_REALTIME);
+ test_timeout(res, &ret, "futex_wait_bitset realtime", ETIMEDOUT);
+
+ /* FUTEX_WAIT_BITSET with CLOCK_MONOTONIC */
+ if (futex_get_abs_timeout(CLOCK_MONOTONIC, &to, timeout_ns))
+ return RET_FAIL;
+ res = futex_wait_bitset(&f1, f1, &to, 1, 0);
+ test_timeout(res, &ret, "futex_wait_bitset monotonic", ETIMEDOUT);
+
+ /* FUTEX_WAIT_REQUEUE_PI with CLOCK_REALTIME */
+ if (futex_get_abs_timeout(CLOCK_REALTIME, &to, timeout_ns))
+ return RET_FAIL;
+ res = futex_wait_requeue_pi(&f1, f1, &futex_pi, &to, FUTEX_CLOCK_REALTIME);
+ test_timeout(res, &ret, "futex_wait_requeue_pi realtime", ETIMEDOUT);
+
+ /* FUTEX_WAIT_REQUEUE_PI with CLOCK_MONOTONIC */
+ if (futex_get_abs_timeout(CLOCK_MONOTONIC, &to, timeout_ns))
+ return RET_FAIL;
+ res = futex_wait_requeue_pi(&f1, f1, &futex_pi, &to, 0);
+ test_timeout(res, &ret, "futex_wait_requeue_pi monotonic", ETIMEDOUT);
+
+ /*
+ * FUTEX_LOCK_PI with CLOCK_REALTIME
+ * Due to historical reasons, FUTEX_LOCK_PI supports only realtime
+ * clock, but requires the caller to not set CLOCK_REALTIME flag.
+ *
+ * If you call FUTEX_LOCK_PI with a monotonic clock, it'll be
+ * interpreted as a realtime clock, and (unless you mess your machine's
+ * time or your time machine) the monotonic clock value is always
+ * smaller than realtime and the syscall will timeout immediately.
+ */
+ if (futex_get_abs_timeout(CLOCK_REALTIME, &to, timeout_ns))
+ return RET_FAIL;
+ res = futex_lock_pi(&futex_pi, &to, 0, 0);
+ test_timeout(res, &ret, "futex_lock_pi realtime", ETIMEDOUT);
+
+ /* Test operations that don't support FUTEX_CLOCK_REALTIME */
+ res = futex_lock_pi(&futex_pi, NULL, 0, FUTEX_CLOCK_REALTIME);
+ test_timeout(res, &ret, "futex_lock_pi invalid timeout flag", ENOSYS);

- print_result(TEST_NAME, ret);
+ ksft_print_cnts();
return ret;
}
--
2.31.1
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