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freeze -- Wait for exiting tasks to complete

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There is a small race between exitings tasks and cgroup freezer:
it can report a pid of exiting process which we will consider
as a zombie and refuse to checkpoint. Lets do a trick instead:
if we meets such task just wait a bit and repeate a freezing.

v3: Use EAGAIN instead of EPERM since EPERM collide
    with general -1 error code.

travis-ci: success for freeze -- Wait for exiting tasks to complete (rev3)
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
This commit is contained in:
Cyrill Gorcunov 2016-10-11 23:14:00 +03:00 • committed by Pavel Emelyanov
parent 4f329dd4b2
commit 172f3e1908
1 changed files with 26 additions and 9 deletions
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35
criu/seize.c
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@ -137,11 +137,16 @@ static int seize_cgroup_tree(char *root_path, const char *state)
snprintf(buf, sizeof(buf), "/proc/%d/exe", pid);
if (stat(buf, &st) == -1 && errno == ENOENT)
continue;
/* fails when meets a zombie */
/*
* fails when meets a zombie, or eixting process:
* there is a small race in a kernel -- the process
* may start exiting and we are trying to freeze it
* before it compete exit procedure. The caller simply
* should wait a bit and try freezing again.
*/
pr_err("zombie found while seizing\n");
fclose(f);
return -1;
return -EAGAIN;
}
}
fclose(f);
@ -154,6 +159,7 @@ static int seize_cgroup_tree(char *root_path, const char *state)
while ((de = readdir(dir))) {
struct stat st;
int ret;
if (dir_dots(de))
continue;
@ -168,10 +174,10 @@ static int seize_cgroup_tree(char *root_path, const char *state)
if (!S_ISDIR(st.st_mode))
continue;
if (seize_cgroup_tree(path, state) < 0) {
ret = seize_cgroup_tree(path, state);
if (ret < 0) {
closedir(dir);
return -1;
return ret;
}
}
closedir(dir);
@ -325,7 +331,7 @@ static int freeze_processes(void)
static const unsigned long step_ms = 100;
unsigned long nr_attempts = (opts.timeout * 1000000) / step_ms;
unsigned long i;
unsigned long i = 0;
const struct timespec req = {
.tv_nsec = step_ms * 1000000,
@ -371,7 +377,7 @@ static int freeze_processes(void)
* not read @tasks pids while freezer in
* transition stage.
*/
for (i = 0; i <= nr_attempts; i++) {
for (; i <= nr_attempts; i++) {
state = get_freezer_state(fd);
if (!state) {
close(fd);
@ -395,7 +401,18 @@ static int freeze_processes(void)
pr_debug("freezing processes: %lu attempts done\n", i);
}
exit_code = seize_cgroup_tree(opts.freeze_cgroup, state);
/*
* Pay attention on @i variable -- it's continuation.
*/
for (; i <= nr_attempts; i++) {
exit_code = seize_cgroup_tree(opts.freeze_cgroup, state);
if (exit_code == -EAGAIN) {
if (alarm_timeouted())
goto err;
nanosleep(&req, NULL);
} else
break;
}
err:
if (exit_code == 0 || freezer_thawed) {