Merge pull request #15670 from dan131riley/unregister-tfile-context

Create a context around TFile::Open() so the context is unregistered …

IOPool/Input/src/InputFile.cc

@@ -18,6 +18,13 @@ namespace edm {
   InputFile::InputFile(char const* fileName, char const* msg, InputType inputType) :
     file_(), fileName_(fileName), reportToken_(0), inputType_(inputType) {
 
+    // ROOT's context management implicitly assumes that a file is opened and
+    // closed on the same thread.  To avoid the problem, we declare a local
+    // TContext object; when it goes out of scope, its destructor unregisters
+    // the context, guaranteeing the context is unregistered in the same thread
+    // it was registered in.  Fixes issue #15524.
+    TDirectory::TContext contextEraser;
+
     logFileAction(msg, fileName);
     file_ = std::unique_ptr<TFile>(TFile::Open(fileName)); // propagate_const<T> has no reset() function
     std::exception_ptr e = edm::threadLocalException::getException();