Add support for reset-on-fork scheduling flag

This patch extends CRIU with support for SCHED_RESET_ON_FORK.

If the SCHED_RESET_ON_FORK flag is set, the following rules apply for
subsequently created children:

- If the calling thread has a scheduling policy of SCHED_FIFO or
SCHED_RR, the policy is reset to SCHED_OTHER in child processes.

- If the calling process has a negative nice value, the nice value
is reset to zero in child processes.

(See 'man 7 sched')

Fixes: #2359

Signed-off-by: Radostin Stoyanov <[email protected]>

criu/cr-dump.c

@@ -157,7 +157,8 @@ static int dump_sched_info(int pid, ThreadCoreEntry *tc)
 	tc->has_sched_policy = true;
 	tc->sched_policy = ret;
 
-	if ((ret == SCHED_RR) || (ret == SCHED_FIFO)) {
+	if ((ret == SCHED_RR) || (ret == SCHED_FIFO) ||
+	    (ret == (SCHED_RR | SCHED_RESET_ON_FORK)) || (ret == (SCHED_FIFO | SCHED_RESET_ON_FORK))) {
 		ret = syscall(__NR_sched_getparam, pid, &sp);
 		if (ret < 0) {
 			pr_perror("Can't get sched param for %d", pid);

criu/cr-restore.c

@@ -3060,6 +3060,8 @@ static int validate_sched_parm(struct rst_sched_param *sp)
 	switch (sp->policy) {
 	case SCHED_RR:
 	case SCHED_FIFO:
+	case (SCHED_RR | SCHED_RESET_ON_FORK):
+	case (SCHED_FIFO | SCHED_RESET_ON_FORK):
 		return ((sp->prio > 0) && (sp->prio < 100));
 	case SCHED_IDLE:
 	case SCHED_OTHER:

test/zdtm/static/sched_policy00.c

@@ -51,7 +51,7 @@ int main(int argc, char **argv)
 	}
 
 	p.sched_priority = param;
-	if (sched_setscheduler(pid, SCHED_RR, &p)) {
+	if (sched_setscheduler(pid, SCHED_RR | SCHED_RESET_ON_FORK, &p)) {
 		pr_perror("Can't set policy");
 		kill(pid, SIGKILL);
 		return -1;
@@ -61,7 +61,7 @@ int main(int argc, char **argv)
 	test_waitsig();
 
 	ret = sched_getscheduler(pid);
-	if (ret != SCHED_RR) {
+	if (ret != (SCHED_RR | SCHED_RESET_ON_FORK)) {
 		fail("Broken/No policy");
 		err++;
 	}