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Freeze fixes and v1 kludges #2545

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Freeze fixes and v1 kludges #2545

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46e0a0f
freeze_processes: fix nr_attempts calculation
kolyshkin Dec 13, 2024
2d3fb7b
freeze_processes: implement kludges for cgroup v1
kolyshkin Dec 13, 2024
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36 changes: 33 additions & 3 deletions criu/seize.c
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Original file line number Diff line number Diff line change
Expand Up @@ -542,7 +542,7 @@
enum freezer_state state = THAWED;

static const unsigned long step_ms = 100;
unsigned long nr_attempts = (opts.timeout * 1000000) / step_ms;
unsigned long nr_attempts = (opts.timeout * 1000) / step_ms;
unsigned long i = 0;

const struct timespec req = {
Expand All @@ -555,7 +555,7 @@
* If timeout is turned off, lets
* wait for at least 10 seconds.
*/
nr_attempts = (10 * 1000000) / step_ms;
nr_attempts = (10 * 1000) / step_ms;
}

pr_debug("freezing processes: %lu attempts with %lu ms steps\n", nr_attempts, step_ms);
Expand Down Expand Up @@ -594,9 +594,39 @@

if (state == FROZEN)
break;
if (alarm_timeouted())
if (alarm_timeouted()) {
pr_err("Unable to freeze cgroup %s (timed out)\n", opts.freeze_cgroup);
goto err;
}
nanosleep(&req, NULL);

if (cgroup_v2)
continue;

/* As per older kernel docs (freezer-subsystem.txt before
* the kernel commit ef9fe980c6fcc1821), if FREEZING is seen,
* userspace should either retry or thaw. While current
* kernel cgroup v1 docs no longer mention a need to retry,
* even recent kernels can't reliably freeze a cgroup v1.
*
* Let's keep asking the kernel to freeze from time to time.
* In addition, do occasional thaw/sleep/freeze.
*
* This is still a game of chances (the real fix belongs to the kernel)
* but these kludges might improve the probability of success.
*
* Cgroup v2 does not have this problem.
*/
switch (i%32) {

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case 30:
freezer_write_state(fd, THAWED);
break;
case 9:
case 20:
case 31:
freezer_write_state(fd, FROZEN);
break;
}
}

if (i > nr_attempts) {
Expand Down
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