tests/cgroup: move cg_wait_for(), cg_prepare_for_wait()

as they will be used by the tests for cgroup killing.

Link: https://lore.kernel.org/r/20210503143922.3093755-4-brauner@kernel.org
Cc: Tejun Heo <tj@kernel.org>
Cc: cgroups@vger.kernel.org
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

tools/testing/selftests/cgroup/cgroup_util.c

@@ -5,10 +5,12 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <linux/limits.h>
+#include <poll.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/inotify.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/wait.h>
@@ -580,3 +582,48 @@ int clone_into_cgroup_run_wait(const char *cgroup)
 	(void)clone_reap(pid, WEXITED);
 	return 0;
 }
+
+int cg_prepare_for_wait(const char *cgroup)
+{
+	int fd, ret = -1;
+
+	fd = inotify_init1(0);
+	if (fd == -1)
+		return fd;
+
+	ret = inotify_add_watch(fd, cg_control(cgroup, "cgroup.events"),
+				IN_MODIFY);
+	if (ret == -1) {
+		close(fd);
+		fd = -1;
+	}
+
+	return fd;
+}
+
+int cg_wait_for(int fd)
+{
+	int ret = -1;
+	struct pollfd fds = {
+		.fd = fd,
+		.events = POLLIN,
+	};
+
+	while (true) {
+		ret = poll(&fds, 1, 10000);
+
+		if (ret == -1) {
+			if (errno == EINTR)
+				continue;
+
+			break;
+		}
+
+		if (ret > 0 && fds.revents & POLLIN) {
+			ret = 0;
+			break;
+		}
+	}
+
+	return ret;
+}

tools/testing/selftests/cgroup/cgroup_util.h

@@ -54,3 +54,5 @@ extern pid_t clone_into_cgroup(int cgroup_fd);
 extern int clone_reap(pid_t pid, int options);
 extern int clone_into_cgroup_run_wait(const char *cgroup);
 extern int dirfd_open_opath(const char *dir);
+extern int cg_prepare_for_wait(const char *cgroup);
+extern int cg_wait_for(int fd);

tools/testing/selftests/cgroup/test_freezer.c

@@ -7,9 +7,7 @@
 #include <unistd.h>
 #include <stdio.h>
 #include <errno.h>
-#include <poll.h>
 #include <stdlib.h>
-#include <sys/inotify.h>
 #include <string.h>
 #include <sys/wait.h>
 
@@ -54,61 +52,6 @@ static int cg_freeze_nowait(const char *cgroup, bool freeze)
 	return cg_write(cgroup, "cgroup.freeze", freeze ? "1" : "0");
 }
 
-/*
- * Prepare for waiting on cgroup.events file.
- */
-static int cg_prepare_for_wait(const char *cgroup)
-{
-	int fd, ret = -1;
-
-	fd = inotify_init1(0);
-	if (fd == -1) {
-		debug("Error: inotify_init1() failed\n");
-		return fd;
-	}
-
-	ret = inotify_add_watch(fd, cg_control(cgroup, "cgroup.events"),
-				IN_MODIFY);
-	if (ret == -1) {
-		debug("Error: inotify_add_watch() failed\n");
-		close(fd);
-		fd = -1;
-	}
-
-	return fd;
-}
-
-/*
- * Wait for an event. If there are no events for 10 seconds,
- * treat this an error.
- */
-static int cg_wait_for(int fd)
-{
-	int ret = -1;
-	struct pollfd fds = {
-		.fd = fd,
-		.events = POLLIN,
-	};
-
-	while (true) {
-		ret = poll(&fds, 1, 10000);
-
-		if (ret == -1) {
-			if (errno == EINTR)
-				continue;
-			debug("Error: poll() failed\n");
-			break;
-		}
-
-		if (ret > 0 && fds.revents & POLLIN) {
-			ret = 0;
-			break;
-		}
-	}
-
-	return ret;
-}
-
 /*
  * Attach a task to the given cgroup and wait for a cgroup frozen event.
  * All transient events (e.g. populated) are ignored.