[Python-checkins] r54924 - in python/branches/release25-maint: Lib/test/test_pty.py Misc/NEWS

[barry.warsaw]

Author: barry.warsaw
Date: Mon Apr 23 03:58:33 2007
New Revision: 54924

Modified:
   python/branches/release25-maint/Lib/test/test_pty.py
   python/branches/release25-maint/Misc/NEWS
Log:
Recommit r54805:

Add code to read from master_fd in the parent, breaking when we get an OSError
(EIO can occur on Linux) or there's no more data to read.  Without this,
test_pty.py can hang on the waitpid() because the child is blocking on the
stdout write.  This will definitely happen on Mac OS X and could potentially
happen on other platforms.  See the comment for details.


Modified: python/branches/release25-maint/Lib/test/test_pty.py
==============================================================================
--- python/branches/release25-maint/Lib/test/test_pty.py	(original)
+++ python/branches/release25-maint/Lib/test/test_pty.py	Mon Apr 23 03:58:33 2007
@@ -115,6 +115,24 @@
     os._exit(4)
 else:
     debug("Waiting for child (%d) to finish."%pid)
+    # In verbose mode, we have to consume the debug output from the child or
+    # the child will block, causing this test to hang in the parent's
+    # waitpid() call.  The child blocks after a platform-dependent amount of
+    # data is written to its fd.  On Linux 2.6, it's 4000 bytes and the child
+    # won't block, but on OS X even the small writes in the child above will
+    # block it.  Also on Linux, the read() will throw an OSError (input/output
+    # error) when it tries to read past the end of the buffer but the child's
+    # already exited, so catch and discard those exceptions.  It's not worth
+    # checking for EIO.
+    while True:
+        try:
+            data = os.read(master_fd, 80)
+        except OSError:
+            break
+        if not data:
+            break
+        sys.stdout.write(data.replace('\r\n', '\n'))
+
     ##line = os.read(master_fd, 80)
     ##lines = line.replace('\r\n', '\n').split('\n')
     ##if False and lines != ['In child, calling os.setsid()',

Modified: python/branches/release25-maint/Misc/NEWS
==============================================================================
--- python/branches/release25-maint/Misc/NEWS	(original)
+++ python/branches/release25-maint/Misc/NEWS	Mon Apr 23 03:58:33 2007
@@ -17,6 +17,9 @@
 
 - tarfile.py: Fix directory names to have only one trailing slash.
 
+- Fix test_pty.py to not hang on OS X (and theoretically other *nixes) when
+  run in verbose mode.
+
 
 What's New in Python 2.5.1?
 =============================