[GitHub] [mesos] abudnik commented on a change in pull request #355: Handle EBUSY when destroying a cgroup.

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abudnik commented on a change in pull request #355: Handle EBUSY when destroying a cgroup.
URL: https://github.com/apache/mesos/pull/355#discussion_r401684158
 
 

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 File path: src/linux/cgroups.cpp
 ##########
 @@ -696,13 +696,24 @@ Try<Nothing> remove(const string& hierarchy, const string& cgroup)
   string path = path::join(hierarchy, cgroup);
 
   // Do NOT recursively remove cgroups.
-  Try<Nothing> rmdir = os::rmdir(path, false);
-  if (rmdir.isError()) {
-    return Error(
+  // TODO The retry was added as a fix for kernel bug
+  // https://lkml.org/lkml/2020/1/15/1349
+  // where calling rmdir on a seemingly empty cgroup can fail
+  // with EBUSY while some tasks are exiting.
+  auto delay = Milliseconds(1);
+  for (auto retry = 10; ;) {
+    Try<Nothing> rmdir = os::rmdir(path, false);
+    if (!rmdir.isError()) {
+      return rmdir;
+    } else if (retry > 0) {
+      os::sleep(delay);
 
 Review comment:
   Note that `os::sleep()` is a blocking call while the `remove()` function is supposed to be non-blocking. Calling a blocking function from a non-blocking context must be avoided if possible.
   
   If the error occurs for the `freezer` cgroup only, [Destroyer::remove](https://github.com/apache/mesos/blob/f8a3dd334934094ec44e07fa350f958d218bc78f/src/linux/cgroups.cpp#L1536-L1555) method can be modified to asynchronously retry "remove cgroup" operation.

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