[GitHub] [arrow] pitrou commented on a change in pull request #12358: ARROW-15593: [C++] Make after-fork ThreadPool reinitialization thread-safe

[GitBox <gi...@apache.org>]

pitrou commented on a change in pull request #12358:
URL: https://github.com/apache/arrow/pull/12358#discussion_r801407952



##########
File path: cpp/src/arrow/util/mutex.cc
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@@ -50,5 +55,31 @@ Mutex::Guard Mutex::Lock() {
 
 Mutex::Mutex() : impl_(new Impl, [](Impl* impl) { delete impl; }) {}
 
+#ifndef _WIN32
+namespace {
+
+struct AfterForkState {
+  // A global instance that will also register the atfork handler when
+  // constructed.
+  static AfterForkState instance;
+
+  // The mutex may be used at shutdown, so make it eternal.
+  // The leak (only in child processes) is a small price to pay for robustness.
+  Mutex* mutex = nullptr;

Review comment:
       Just for the record, no process will be larger because of this leak. Perhaps I should have put "leak" in quotes, because regardless of using `unique_ptr` or not, the mutex will be destroyed at process exit. The difference is mainly in code hygiene, and also some sanitizers may report it as an actual leak (memory that wasn't deallocated before process exit).




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