Always use cgroups in runguard.

There is no benefit in not using them, the library needs to be installed
anyway to be able to compile runguard and it makes the flow in runguard
more consistent.

Author: meisterT

judge/runguard.c

@@ -375,8 +375,6 @@ Run COMMAND with restrictions.\n\
 Note that root privileges are needed for the `root' and `user' options.\n\
 If `user' is set, then `group' defaults to the same to prevent security\n\
 issues, since otherwise the process would retain group root permissions.\n\
-Additionally, Linux cgroup support is required for the `memsize', `cpuset'\n\
-and `cputime' options, and to report actual memory usage.\n\
 The COMMAND path is relative to the changed ROOT directory if specified.\n\
 TIME may be specified as a float; two floats separated by `:' are treated\n\
 as soft and hard limits. The runtime written to file is that of the last\n\
@@ -444,22 +442,10 @@ void output_exit_time(int exitcode, double cpudiff)
 	write_meta("time-result","%s",output_timelimit_str[timelimit_reached]);
 }
 
-/* Return whether we need to use cgroups. This is checked in the
- * cgroup_* functions below. If not used they return without
- * performing any action.
- */
-int use_cgroup()
-{
-	return use_cputime || memsize!=RLIM_INFINITY ||
-	    ( cpuset!=NULL && strlen(cpuset)>0 );
-}
-
 void check_remaining_procs()
 {
     char path[1024];
 
-    if ( !use_cgroup() ) return;
-
     snprintf(path, 1023, "/sys/fs/cgroup/cpuacct%scgroup.procs", cgroupname);
     FILE *file = fopen(path, "r");
     if (file == NULL) {
@@ -480,8 +466,6 @@ void output_cgroup_stats(double *cputime)
 	struct cgroup *cg;
 	struct cgroup_controller *cg_controller;
 
-	if ( !use_cgroup() ) return;
-
 	if ( (cg = cgroup_new_cgroup(cgroupname))==NULL ) error(0,"cgroup_new_cgroup");
 	if ((ret = cgroup_get_cgroup(cg)) != 0) error(ret,"get cgroup information");
 
@@ -512,8 +496,6 @@ void cgroup_create()
 	struct cgroup *cg;
 	struct cgroup_controller *cg_controller;
 
-	if ( !use_cgroup() ) return;
-
 	cg = cgroup_new_cgroup(cgroupname);
 	if (!cg) error(0,"cgroup_new_cgroup");
 
@@ -560,8 +542,6 @@ void cgroup_attach()
 	int ret;
 	struct cgroup *cg;
 
-	if ( !use_cgroup() ) return;
-
 	cg = cgroup_new_cgroup(cgroupname);
 	if (!cg) error(0,"cgroup_new_cgroup");
 
@@ -579,8 +559,6 @@ void cgroup_kill()
 	void *handle = NULL;
 	pid_t pid;
 
-	if ( !use_cgroup() ) return;
-
 	/* kill any remaining tasks, and wait for them to be gone */
 	while(1) {
 		ret = cgroup_get_task_begin(cgroupname, "memory", &handle, &pid);
@@ -595,8 +573,6 @@ void cgroup_delete()
 	int ret;
 	struct cgroup *cg;
 
-	if ( !use_cgroup() ) return;
-
 	cg = cgroup_new_cgroup(cgroupname);
 	if (!cg) error(0,"cgroup_new_cgroup");
 
@@ -1198,11 +1174,9 @@ int main(int argc, char **argv)
 		}
 	}
 	/* Make libcgroup ready for use */
-	if ( use_cgroup() ) {
-		ret = cgroup_init();
-		if ( ret!=0 ) {
-			error(0,"libcgroup initialization failed: %s(%d)\n", cgroup_strerror(ret), ret);
-		}
+	ret = cgroup_init();
+	if ( ret!=0 ) {
+		error(0,"libcgroup initialization failed: %s(%d)\n", cgroup_strerror(ret), ret);
 	}
 	/* Define the cgroup name that we will use and make sure it will
 	 * be unique. Note: group names must have slashes!