cgroup-util: make cg_read_pid skip zeros

src/basic/cgroup-util.c

@@ -103,19 +103,22 @@ int cg_read_pid(FILE *f, pid_t *ret) {
  assert(f);
  assert(ret);
 
- errno = 0;
- if (fscanf(f, "%lu", &ul) != 1) {
+ /* In some environments(WSL), the pid list contains a bunch of zeros.
+ * Maybe the kernel is hiding pids from other containerized instances.
+ * Just skip over those and move on. */
+ do {
+ errno = 0;
+ if (fscanf(f, "%lu", &ul) != 1) {
 
- if (feof(f)) {
- *ret = 0;
- return 0;
- }
+  if (feof(f)) {
+  *ret = 0;
+  return 0;
+  }
 
- return errno_or_else(EIO);
- }
+ return errno_or_else(EIO);
+ }
+ } while (ul == 0);
 
- if (ul <= 0)
- return -EIO;
  if (ul > PID_T_MAX)
  return -EIO;