criu: Allow disabling freeze cgroups

Some plugins (e.g., CUDA) may not function correctly when processes are
frozen using cgroups. This change introduces a mechanism to disable the
use of freeze cgroups during process seizing, even if explicitly
requested via the --freeze-cgroup option.

The CUDA plugin is updated to utilize this new mechanism to ensure
compatibility.

Signed-off-by: Andrei Vagin <[email protected]>

criu/include/seize.h

@@ -8,5 +8,6 @@ extern bool alarm_timeouted(void);
 
 extern char *task_comm_info(pid_t pid, char *comm, size_t size);
 extern char *__task_comm_info(pid_t pid);
+extern void dont_use_freeze_cgroup(void);
 
 #endif

criu/seize.c

@@ -967,6 +967,19 @@ static int cgroup_version(void)
 	return -1;
 }
 
+static bool freeze_cgroup_disabled;
+
+/*
+ * Disables the use of freeze cgroups for process seizing, even if explicitly
+ * requested via the --freeze-cgroup option. This is necessary for plugins
+ * (e.g., CUDA) that do not function correctly when processes are frozen using
+ * cgroups.
+ */
+void __attribute__((used)) dont_use_freeze_cgroup(void)
+{
+	freeze_cgroup_disabled = true;
+}
+
 int collect_pstree(void)
 {
 	pid_t pid = root_item->pid->real;
@@ -993,12 +1006,14 @@ int collect_pstree(void)
 
 	pr_debug("Detected cgroup V%d freezer\n", cgroup_v2 ? 2 : 1);
 
-	if (opts.freeze_cgroup && freeze_processes())
-		goto err;
-
-	if (!opts.freeze_cgroup && compel_interrupt_task(pid)) {
-		set_cr_errno(ESRCH);
-		goto err;
+	if (opts.freeze_cgroup && !freeze_cgroup_disabled) {
+		if (freeze_processes())
+			goto err;
+	} else {
+		if (compel_interrupt_task(pid)) {
+			set_cr_errno(ESRCH);
+			goto err;
+		}
 	}
 
 	ret = compel_wait_task(pid, -1, parse_pid_status, NULL, &creds.s, NULL);

plugins/cuda/cuda_plugin.c

@@ -483,6 +483,8 @@ int cuda_plugin_init(int stage)
 		INIT_LIST_HEAD(&cuda_pids);
 	}
 
+	dont_use_freeze_cgroup();
+
 	return 0;
 }