selftests: futex: Add futex wait test

There are three different strategies to uniquely identify a futex in the
kernel:

 - Private futexes: uses the pointer to mm_struct and the page address

 - Shared futexes: checks if the page containing the address is a PageAnon:
   - If it is, uses the same data as a private futexes
   - If it isn't, uses an inode sequence number from struct inode and
      the page's index

Create a selftest to check those three paths and basic wait/wake
mechanism.
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/20210531165036.41468-2-andrealmeid@collabora.com

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

@@ -6,3 +6,4 @@ futex_wait_private_mapped_file
 futex_wait_timeout
 futex_wait_uninitialized_heap
 futex_wait_wouldblock
+futex_wait

tools/testing/selftests/futex/functional/Makefile

@@ -15,7 +15,8 @@ TEST_GEN_FILES := \
 	futex_requeue_pi_signal_restart \
 	futex_requeue_pi_mismatched_ops \
 	futex_wait_uninitialized_heap \
-	futex_wait_private_mapped_file
+	futex_wait_private_mapped_file \
+	futex_wait
 
 TEST_PROGS := run.sh
 

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

+// 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 <sys/shm.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include "logging.h"
+#include "futextest.h"
+
+#define TEST_NAME "futex-wait"
+#define timeout_ns  30000000
+#define WAKE_WAIT_US 10000
+#define SHM_PATH "futex_shm_file"
+
+void *futex;
+
+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);
+}
+
+static void *waiterfn(void *arg)
+{
+	struct timespec to;
+	unsigned int flags = 0;
+
+	if (arg)
+		flags = *((unsigned int *) arg);
+
+	to.tv_sec = 0;
+	to.tv_nsec = timeout_ns;
+
+	if (futex_wait(futex, 0, &to, flags))
+		printf("waiter failed errno %d\n", errno);
+
+	return NULL;
+}
+
+int main(int argc, char *argv[])
+{
+	int res, ret = RET_PASS, fd, c, shm_id;
+	u_int32_t f_private = 0, *shared_data;
+	unsigned int flags = FUTEX_PRIVATE_FLAG;
+	pthread_t waiter;
+	void *shm;
+
+	futex = &f_private;
+
+	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(3);
+	ksft_print_msg("%s: Test futex_wait\n", basename(argv[0]));
+
+	/* Testing a private futex */
+	info("Calling private futex_wait on futex: %p\n", futex);
+	if (pthread_create(&waiter, NULL, waiterfn, (void *) &flags))
+		error("pthread_create failed\n", errno);
+
+	usleep(WAKE_WAIT_US);
+
+	info("Calling private futex_wake on futex: %p\n", futex);
+	res = futex_wake(futex, 1, FUTEX_PRIVATE_FLAG);
+	if (res != 1) {
+		ksft_test_result_fail("futex_wake private returned: %d %s\n",
+				      errno, strerror(errno));
+		ret = RET_FAIL;
+	} else {
+		ksft_test_result_pass("futex_wake private succeeds\n");
+	}
+
+	/* Testing an anon page shared memory */
+	shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666);
+	if (shm_id < 0) {
+		perror("shmget");
+		exit(1);
+	}
+
+	shared_data = shmat(shm_id, NULL, 0);
+
+	*shared_data = 0;
+	futex = shared_data;
+
+	info("Calling shared (page anon) futex_wait on futex: %p\n", futex);
+	if (pthread_create(&waiter, NULL, waiterfn, NULL))
+		error("pthread_create failed\n", errno);
+
+	usleep(WAKE_WAIT_US);
+
+	info("Calling shared (page anon) futex_wake on futex: %p\n", futex);
+	res = futex_wake(futex, 1, 0);
+	if (res != 1) {
+		ksft_test_result_fail("futex_wake shared (page anon) returned: %d %s\n",
+				      errno, strerror(errno));
+		ret = RET_FAIL;
+	} else {
+		ksft_test_result_pass("futex_wake shared (page anon) succeeds\n");
+	}
+
+
+	/* Testing a file backed shared memory */
+	fd = open(SHM_PATH, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
+	if (fd < 0) {
+		perror("open");
+		exit(1);
+	}
+
+	if (ftruncate(fd, sizeof(f_private))) {
+		perror("ftruncate");
+		exit(1);
+	}
+
+	shm = mmap(NULL, sizeof(f_private), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (shm == MAP_FAILED) {
+		perror("mmap");
+		exit(1);
+	}
+
+	memcpy(shm, &f_private, sizeof(f_private));
+
+	futex = shm;
+
+	info("Calling shared (file backed) futex_wait on futex: %p\n", futex);
+	if (pthread_create(&waiter, NULL, waiterfn, NULL))
+		error("pthread_create failed\n", errno);
+
+	usleep(WAKE_WAIT_US);
+
+	info("Calling shared (file backed) futex_wake on futex: %p\n", futex);
+	res = futex_wake(shm, 1, 0);
+	if (res != 1) {
+		ksft_test_result_fail("futex_wake shared (file backed) returned: %d %s\n",
+				      errno, strerror(errno));
+		ret = RET_FAIL;
+	} else {
+		ksft_test_result_pass("futex_wake shared (file backed) succeeds\n");
+	}
+
+	/* Freeing resources */
+	shmdt(shared_data);
+	munmap(shm, sizeof(f_private));
+	remove(SHM_PATH);
+	close(fd);
+
+	ksft_print_cnts();
+	return ret;
+}

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

@@ -73,3 +73,6 @@ echo
 echo
 ./futex_wait_uninitialized_heap $COLOR
 ./futex_wait_private_mapped_file $COLOR
+
+echo
+./futex_wait $COLOR