[Python-checkins] cpython (3.2): Fixes issue #15756: subprocess.poll() now properly handles errno.ECHILD

Sat Sep 29 20:58:45 CEST 2012

http://hg.python.org/cpython/rev/484c50bf445c
changeset: 79266:484c50bf445c
branch: 3.2
parent: 79224:70af6b53b52a
user: Gregory P. Smith <greg at krypto.org>
date: Sat Sep 29 11:40:38 2012 -0700
summary:
 Fixes issue #15756: subprocess.poll() now properly handles errno.ECHILD
to return a returncode of 0 when the child has already exited or cannot
be waited on.
files:
 Lib/subprocess.py | 9 +++++++-
 Lib/test/subprocessdata/sigchild_ignore.py | 11 +++++++++-
 Misc/NEWS | 4 +++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/Lib/subprocess.py b/Lib/subprocess.py
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -1400,9 +1400,16 @@
 pid, sts = _waitpid(self.pid, _WNOHANG)
 if pid == self.pid:
 self._handle_exitstatus(sts)
- except _os_error:
+ except _os_error as e:
 if _deadstate is not None:
 self.returncode = _deadstate
+ elif e.errno == errno.ECHILD:
+ # This happens if SIGCLD is set to be ignored or
+ # waiting for child processes has otherwise been
+ # disabled for our process. This child is dead, we
+ # can't get the status.
+ # http://bugs.python.org/issue15756
+ self.returncode = 0
 return self.returncode
 
 
diff --git a/Lib/test/subprocessdata/sigchild_ignore.py b/Lib/test/subprocessdata/sigchild_ignore.py
--- a/Lib/test/subprocessdata/sigchild_ignore.py
+++ b/Lib/test/subprocessdata/sigchild_ignore.py
@@ -1,6 +1,15 @@
-import signal, subprocess, sys
+import signal, subprocess, sys, time
 # On Linux this causes os.waitpid to fail with OSError as the OS has already
 # reaped our child process. The wait() passing the OSError on to the caller
 # and causing us to exit with an error is what we are testing against.
 signal.signal(signal.SIGCHLD, signal.SIG_IGN)
 subprocess.Popen([sys.executable, '-c', 'print("albatross")']).wait()
+# Also ensure poll() handles an errno.ECHILD appropriately.
+p = subprocess.Popen([sys.executable, '-c', 'print("albatross")'])
+num_polls = 0
+while p.poll() is None:
+ # Waiting for the process to finish.
+ time.sleep(0.01) # Avoid being a CPU busy loop.
+ num_polls += 1
+ if num_polls > 3000:
+ raise RuntimeError('poll should have returned 0 within 30 seconds')
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -123,6 +123,10 @@
 Library
 -------
 
+- Issue #15756: subprocess.poll() now properly handles errno.ECHILD to
+ return a returncode of 0 when the child has already exited or cannot
+ be waited on.
+
 - Issue #12376: Pass on parameters in TextTestResult.__init__ super call
 
 - Issue #15222: Insert blank line after each message in mbox mailboxes
-- 
Repository URL: http://hg.python.org/cpython
