Merge issue #12352: Fix a deadlock in multiprocessing.Heap when a block is

freed by the garbage collector while the Heap lock is held.

diff --cc Lib/test/test_multiprocessing.py
Simple merge

diff --cc Misc/NEWS
index 6e0882b962df757e84e9fe04d16f7b57dd10aa8e,423d7ec3e0262a1b3b26072cab0567219da448a6..06932608adb5328cb31824afda6c361b6d3588c2
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -200,13 -25,9 +200,16 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #12352: Fix a deadlock in multiprocessing.Heap when a block is freed by
+   the garbage collector while the Heap lock is held.
+ 
 +- Issue #12462: time.sleep() now calls immediatly the (Python) signal handler
 +  if it is interrupted by a signal, instead of having to wait until the next
 +  instruction.
 +
 +- Issue #12442: new shutil.disk_usage function, providing total, used and free
 +  disk space statistics.
 +
  - Issue #12451: The XInclude default loader of xml.etree now decodes files from
    UTF-8 instead of the locale encoding if the encoding is not specified. It now
    also opens XML files for the parser in binary mode instead of the text mode