seize: Take --timeout option into account when freezing processes

When we're freezing processes we don't count on anything but
rather do 5 attempts with constantly increasing delay.

Lets rather do the following:

 - take --timeout option into account (which is 5 seconds
   by default) and split it into 100 ms steps;

 - when frezing processes check freezer status every 100 ms.

Same time it looks that 5 seconds by default is too small
for high loaded containers. Lets increase it to 10 seconds
by default.

[ skinsbursky@:
Frankly speaking, in this particular case increasing intervals are not nice.
This is not a network issue or something.
Usually freezing takes less than a second, but more, that, say 200ms.
Otherwise it takes quite o lot of time.
If step size is growing all the time, in most of the cases criu will
waste hundreds of milliseconds between iterX (say, third) and (iterX+1)
because of the growing step size.
100ms step looks solid enough: not to small to produce a lot of syscalls
and not to large to waste a lot of time.
With previous scheme freezing was usually taking half a second more that
it should because of this growing step.

[ gorcunov@:
You won't belive, but been able to sepcify --timeout 0 here allowed
me and Stas to catch serieous problem in freezer code.

https://lkml.org/lkml/2016/8/3/317

Without this feature we would have to patch criu instead. So you know,
this would be great to keep it for catching more kernel bugs ;)
Reported-by: Stanislav Kinsburskiy <skinsbursky@virtuozzo.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/include/cr_options.h

@@ -38,7 +38,7 @@ struct cg_root_opt {
  */
 #define DEFAULT_GHOST_LIMIT	(1 << 20)
 
-#define DEFAULT_TIMEOUT		5
+#define DEFAULT_TIMEOUT		10
 
 struct irmap;
 

criu/seize.c

@@ -319,10 +319,30 @@ static int log_unfrozen_stacks(char *root)
 
 static int freeze_processes(void)
 {
-	int i, fd, exit_code = -1;
+	int fd, exit_code = -1;
 	char path[PATH_MAX];
 	const char *state = thawed;
 
+	static const unsigned long step_ms = 100;
+	unsigned long nr_attempts = (opts.timeout * 1000000) / step_ms;
+	unsigned long i;
+
+	const struct timespec req = {
+		.tv_nsec	= step_ms * 1000000,
+		.tv_sec		= 0,
+	};
+
+	if (unlikely(!nr_attempts)) {
+		/*
+		 * If timeout is turned off, lets
+		 * wait for at least 10 seconds.
+		 */
+		nr_attempts = (10 * 1000000) / step_ms;
+	}
+
+	pr_debug("freezing processes: %lu attempst with %lu ms steps\n",
+		 nr_attempts, step_ms);
+
 	snprintf(path, sizeof(path), "%s/freezer.state", opts.freeze_cgroup);
 	fd = open(path, O_RDWR);
 	if (fd < 0) {
@@ -350,10 +370,7 @@ static int freeze_processes(void)
 	 * freezer.state.
 	 * Here is one extra attempt to check that everything are frozen.
 	 */
-	for (i = 0; i <= NR_ATTEMPTS; i++) {
-		struct timespec req = {};
-		u64 timeout;
-
+	for (i = 0; i <= nr_attempts; i++) {
 		if (seize_cgroup_tree(opts.freeze_cgroup, state) < 0)
 			goto err;
 
@@ -376,13 +393,10 @@ static int freeze_processes(void)
 		if (alarm_timeouted())
 			goto err;
 
-		timeout = 100000000 * (i + 1); /* 100 msec */
-		req.tv_nsec = timeout % 1000000000;
-		req.tv_sec = timeout / 1000000000;
 		nanosleep(&req, NULL);
 	}
 
-	if (i > NR_ATTEMPTS) {
+	if (i > nr_attempts) {
 		pr_err("Unable to freeze cgroup %s\n", opts.freeze_cgroup);
 
 		if (!pr_quelled(LOG_DEBUG))
@@ -391,6 +405,7 @@ static int freeze_processes(void)
 		goto err;
 	}
 
+	pr_debug("freezing processes: %lu attempts done\n", i);
 	exit_code = 0;
 err:
 	if (exit_code == 0 || freezer_thawed) {