selftests: futex: Add futex compare requeue test

Add testing for futex_cmp_requeue(). The first test just requeues from one
waiter to another one, and wakes it. The second performs both wake and
requeue, and checks the return values to see if the operation woke/requeued
the expected number of waiters.

Signed-off-by: André Almeida <andrealmeid@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Link: https://lore.kernel.org/r/20210531165036.41468-3-andrealmeid@collabora.com

tools/testing/selftests/futex/functional/.gitignore

@@ -7,3 +7,4 @@ futex_wait_timeout
 futex_wait_uninitialized_heap
 futex_wait_wouldblock
 futex_wait
+futex_requeue

tools/testing/selftests/futex/functional/Makefile

@@ -16,7 +16,8 @@ TEST_GEN_FILES := \
 	futex_requeue_pi_mismatched_ops \
 	futex_wait_uninitialized_heap \
 	futex_wait_private_mapped_file \
-	futex_wait
+	futex_wait \
+	futex_requeue
 
 TEST_PROGS := run.sh
 

tools/testing/selftests/futex/functional/futex_requeue.c

@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright Collabora Ltd., 2021
+ *
+ * futex cmp requeue test by André Almeida <andrealmeid@collabora.com>
+ */
+
+#include <pthread.h>
+#include <limits.h>
+#include "logging.h"
+#include "futextest.h"
+
+#define TEST_NAME "futex-requeue"
+#define timeout_ns  30000000
+#define WAKE_WAIT_US 10000
+
+volatile futex_t *f1;
+
+void usage(char *prog)
+{
+	printf("Usage: %s\n", prog);
+	printf("  -c	Use color\n");
+	printf("  -h	Display this help message\n");
+	printf("  -v L	Verbosity level: %d=QUIET %d=CRITICAL %d=INFO\n",
+	       VQUIET, VCRITICAL, VINFO);
+}
+
+void *waiterfn(void *arg)
+{
+	struct timespec to;
+
+	to.tv_sec = 0;
+	to.tv_nsec = timeout_ns;
+
+	if (futex_wait(f1, *f1, &to, 0))
+		printf("waiter failed errno %d\n", errno);
+
+	return NULL;
+}
+
+int main(int argc, char *argv[])
+{
+	pthread_t waiter[10];
+	int res, ret = RET_PASS;
+	int c, i;
+	volatile futex_t _f1 = 0;
+	volatile futex_t f2 = 0;
+
+	f1 = &_f1;
+
+	while ((c = getopt(argc, argv, "cht:v:")) != -1) {
+		switch (c) {
+		case 'c':
+			log_color(1);
+			break;
+		case 'h':
+			usage(basename(argv[0]));
+			exit(0);
+		case 'v':
+			log_verbosity(atoi(optarg));
+			break;
+		default:
+			usage(basename(argv[0]));
+			exit(1);
+		}
+	}
+
+	ksft_print_header();
+	ksft_set_plan(2);
+	ksft_print_msg("%s: Test futex_requeue\n",
+		       basename(argv[0]));
+
+	/*
+	 * Requeue a waiter from f1 to f2, and wake f2.
+	 */
+	if (pthread_create(&waiter[0], NULL, waiterfn, NULL))
+		error("pthread_create failed\n", errno);
+
+	usleep(WAKE_WAIT_US);
+
+	info("Requeuing 1 futex from f1 to f2\n");
+	res = futex_cmp_requeue(f1, 0, &f2, 0, 1, 0);
+	if (res != 1) {
+		ksft_test_result_fail("futex_requeue simple returned: %d %s\n",
+				      res ? errno : res,
+				      res ? strerror(errno) : "");
+		ret = RET_FAIL;
+	}
+
+
+	info("Waking 1 futex at f2\n");
+	res = futex_wake(&f2, 1, 0);
+	if (res != 1) {
+		ksft_test_result_fail("futex_requeue simple returned: %d %s\n",
+				      res ? errno : res,
+				      res ? strerror(errno) : "");
+		ret = RET_FAIL;
+	} else {
+		ksft_test_result_pass("futex_requeue simple succeeds\n");
+	}
+
+
+	/*
+	 * Create 10 waiters at f1. At futex_requeue, wake 3 and requeue 7.
+	 * At futex_wake, wake INT_MAX (should be exactly 7).
+	 */
+	for (i = 0; i < 10; i++) {
+		if (pthread_create(&waiter[i], NULL, waiterfn, NULL))
+			error("pthread_create failed\n", errno);
+	}
+
+	usleep(WAKE_WAIT_US);
+
+	info("Waking 3 futexes at f1 and requeuing 7 futexes from f1 to f2\n");
+	res = futex_cmp_requeue(f1, 0, &f2, 3, 7, 0);
+	if (res != 10) {
+		ksft_test_result_fail("futex_requeue many returned: %d %s\n",
+				      res ? errno : res,
+				      res ? strerror(errno) : "");
+		ret = RET_FAIL;
+	}
+
+	info("Waking INT_MAX futexes at f2\n");
+	res = futex_wake(&f2, INT_MAX, 0);
+	if (res != 7) {
+		ksft_test_result_fail("futex_requeue many returned: %d %s\n",
+				      res ? errno : res,
+				      res ? strerror(errno) : "");
+		ret = RET_FAIL;
+	} else {
+		ksft_test_result_pass("futex_requeue many succeeds\n");
+	}
+
+	ksft_print_cnts();
+	return ret;
+}

tools/testing/selftests/futex/functional/run.sh

@@ -76,3 +76,6 @@ echo
 
 echo
 ./futex_wait $COLOR
+
+echo
+./futex_requeue $COLOR