Function remove

src/linux/cgroups.cpp:274–313

Removes a cgroup from a given hierachy. @param hierarchy Path to hierarchy root. @param cgroup Path of the cgroup relative to the hierarchy root. @return Some if the operation succeeds. Error if the operation fails.

// @return  Some if the operation succeeds.
//          Error if the operation fails.
Future<Nothing> remove(const string& hierarchy, const string& cgroup)
{
  const string path = path::join(hierarchy, cgroup);

  // We retry on EBUSY as a workaround for kernel bug
  // https://lkml.org/lkml/2020/1/15/1349 and others which cause rmdir to fail
  // with EBUSY even though the cgroup appears empty.

  Duration delay = Duration::zero();

  return loop(
      [=]() mutable {
        auto timeout = process::after(delay);
        delay = (delay == Duration::zero()) ? Milliseconds(1) : delay * 2;
        return timeout;
      },
      [=](const Nothing&) mutable -> Future<ControlFlow<Nothing>> {
        if (::rmdir(path.c_str()) == 0) {
          return process::Break();
        } else if (errno == EBUSY) {
          LOG(WARNING) << "Removal of cgroup " << path
                       << " failed with EBUSY, will try again";

          return process::Continue();
        } else {
          // If the `cgroup` still exists in the hierarchy, treat this as
          // an error; otherwise, treat this as a success since the `cgroup`
          // has actually been cleaned up.
          // Save the error string as os::exists may clobber errno.
          const string error = os::strerror(errno);
          if (os::exists(path::join(hierarchy, cgroup))) {
            return Failure(
                "Failed to remove directory '" + path + "': " + error);
          }

          return process::Break();
        }
      }
    );
}


// Removes a list of cgroups from a given hierachy.