From patchwork Thu Jan 21 20:42:04 2016
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Subject: [STABLE] run-tests: fix race condition
From: Laurent Charignon <lcharignon@fb.com>
X-Patchwork-Id: 12862
Message-Id: <0f975bc6ef3c310d22fb.1453408924@dev5073.prn1.facebook.com>
To: <mercurial-devel@selenic.com>
Date: Thu, 21 Jan 2016 12:42:04 -0800

# HG changeset patch
# User Laurent Charignon <lcharignon@fb.com>
# Date 1453408632 28800
#      Thu Jan 21 12:37:12 2016 -0800
# Branch stable
# Node ID 0f975bc6ef3c310d22fb3016a3204e73bd2fdb1c
# Parent  f62dea3f36975b3daac82e9dcd0ec964cf30c2a7
run-tests: fix race condition

Before this patch, it was possible for run-tests to crash on a race condition.
The race condition happens in the following case:
- the last test finishes and calls: done.put(None)
- the context switches to the main thread that clears the channels list
- the context switches to the last test mentioned above, it tries to access
channels[channel] and crashes
This happened to me while running run-tests.

This patch fixes the issue by clearing the channel before considering that the
test is done.

diff --git a/tests/run-tests.py b/tests/run-tests.py
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -1526,13 +1526,13 @@
             channels[channel] = "=" + test.name[5:].split(".")[0]
             try:
                 test(result)
+                channels[channel] = ''
                 done.put(None)
             except KeyboardInterrupt:
-                pass
+                channels[channel] = ''
             except: # re-raises
                 done.put(('!', test, 'run-test raised an error, see traceback'))
                 raise
-            channels[channel] = ''
 
         def stat():
             count = 0