From e3ab89057da44d73517d6e59841f75322d3f9f99 Mon Sep 17 00:00:00 2001
From: Paul McCarthy <pauld.mccarthy@gmail.com>
Date: Mon, 17 Apr 2017 20:49:47 +0100
Subject: [PATCH] Very subtle bugfix in TaskThread, which was causing
ImageWrapper unit tests to lock up (as thousands of TaskThreads were being
created, and not destroyed)
---
fsl/utils/async.py | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
diff --git a/fsl/utils/async.py b/fsl/utils/async.py
index cd9f05e74..61e5aca90 100644
--- a/fsl/utils/async.py
+++ b/fsl/utils/async.py
@@ -691,6 +691,34 @@ class TaskThread(threading.Thread):
while True:
try:
+ # Clear ref to previous task if any. This
+ # is very important, because otherwise, if
+ # no tasks get posted to the queue, this
+ # loop will spin on queue.Empty exceptions,
+ # and the previous Task object will preserve
+ # a hanging ref to its function/method. Not
+ # ideal if the ref is to a method of the
+ # object which created this TaskThread, and
+ # needs to be GC'd!
+ task = None
+
+ # An example: Without clearing the task
+ # reference, the following code would
+ # result in the TaskThread spinning on empty
+ # forever, and would prevent the Blah
+ # instance from being GC'd:
+ #
+ # class Blah(object):
+ # def __init__(self):
+ # tt = TaskThraed()
+ # tt.enqueue(self.method)
+ # tt.start()
+ #
+ # def method(self):
+ # pass
+ #
+ # b = Blah()
+ # del b
task = self.__q.get(timeout=1)
except queue.Empty:
--
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