Subsystem::Subsystem(const std::string& name, const std::string& mountPoint) : mName(name)
{
if (mName.empty()) {
const std::string msg = "CGroup name is empty";
LOGE(msg);
throw CGroupException(msg);
}
//find mount point for a name
std::ifstream fileStream("/proc/mounts");
if (!fileStream.good()) {
const std::string msg = "Failed to open /proc/mounts";
LOGE(msg);
throw CGroupException(msg);
}
std::string line;
while (std::getline(fileStream, line).good()) {
std::istringstream iss(line);
auto it = std::istream_iterator<std::string>(iss);
it++; //skip device name (fake for cgroup filesystem type)
std::string path = *it++; //mount point
if (!mountPoint.empty() && mountPoint != path) {
continue;
}
if (it->compare("cgroup") != 0) { //filesystem type
continue;
}
it++; //skip filesystem type
if (it->find(mName) != std::string::npos) {
mPath = std::move(path);
break;
}
}
}
void Subsystem::attach(const std::string& path, const std::vector<std::string>& subs)
{
if (path.empty()) {
const std::string msg = "Trying attach to emtpy path";
LOGE(msg);
throw CGroupException(msg);
}
if (!utils::createDirs(path,0777)) {
throw CGroupException("Can't create mount point: " + path + ", " + utils::getSystemErrorMessage());
}
if (!utils::mount("cgroup", path, "cgroup", 0, utils::join(subs,","))) {
throw CGroupException("Can't mount cgroup: " + path + ", " + utils::getSystemErrorMessage());
}
}
std::vector<std::string> Subsystem::getCGroups(pid_t pid)
{
std::ifstream fileStream("/proc/" + std::to_string(pid) + "/cgroup");
if (!fileStream.good()) {
const std::string msg = "Failed to open /proc/<pid>/cgroup";
LOGE(msg);
throw CGroupException(msg);
}
std::vector<std::string> subs;
std::string line;
while (std::getline(fileStream, line).good()) {
if (utils::beginsWith(line, "#")) {
continue;
}
// istream_iterator does not support delimiter
std::istringstream iss(line);
std::string n, p;
std::getline(iss, n, ':'); // ignore
std::getline(iss, n, ':'); // subsystem name
std::getline(iss, p, ':'); // cgroup path
subs.push_back(n + ":" + p);
}
return subs;
}
const std::string& Subsystem::getMountPoint() const
{
if (!isAttached()) {
const std::string msg = "CGroup '" + mName + "' is not attached";
LOGE(msg);
throw CGroupException(msg);
}
return mPath;
}
bool Subsystem::isAvailable() const
{
if (mName.empty()) {
const std::string msg = "CGroup name is empty";
LOGE(msg);
throw CGroupException(msg);
}
std::vector<std::string> av = availableSubsystems();
return std::find(av.begin(), av.end(), mName) != av.end();
}
std::string getCGroupName(const std::string& s)
{
auto p = s.find(':');
if (p == std::string::npos) {
const std::string msg = "wrong cgroup format " + s;
LOGE(msg);
throw CGroupException(msg);
}
return s.substr(p + 1);
}
void Subsystem::detach(const std::string& path)
{
LOGI("Subsystem::detach " + path);
// if happens (1/100) umount fails with EBUSY
// in fact I don't know why this filesystem (subsystem hierarchy) can be busy
// probably modyfying sth in hierarchy by other process in the system
// following can be considered as workarround
for (int retry = 10; retry > 0; ) {
if (utils::umount(path)) {
if (retry != 10) {
LOGW("umount done afer " << (10 - retry) << " tries");
}
return ;
}
LOGW("umount retry...");
--retry;
usleep(1);
}
throw CGroupException("Can't umount cgroup: " + path + ", " + utils::getSystemErrorMessage());
}
std::vector<std::string> Subsystem::availableSubsystems()
{
std::ifstream fileStream("/proc/cgroups");
if (!fileStream.good()) {
const std::string msg = "Failed to open /proc/cgroups";
LOGE(msg);
throw CGroupException(msg);
}
std::vector<std::string> subs;
std::string line;
while (std::getline(fileStream, line).good()) {
if (utils::beginsWith(line, "#")) {
continue;
}
std::istringstream iss(line);
auto it = std::istream_iterator<std::string>(iss);
std::string n = *it++; //subsystem name
subs.push_back(n);
}
return subs;
}