Restore SIGPIPE default action for subprocesses

Python ignores SIGPIPE on startup, because it prefers to check every
write and raise an IOError exception rather than taking the signal. Most
Unix subprocesses don't expect to work this way. This patch (adapted
from Colin Watson's post at http://tinyurl.com/2a7mzh5) sets SIGPIPE
back to the default action for quantum.agent.linux.utils.execute,
quantum.common.utils.execute and quantum-rootwrap created subprocesses.

Fixes bug 1053364

Change-Id: Ib805f1f8846c245b75a5ea64278c840b823c1fb2

bin/quantum-rootwrap

@@ -38,6 +38,7 @@
 
 import ConfigParser
 import os
+import signal
 import subprocess
 import sys
 
@@ -47,6 +48,12 @@ RC_NOCOMMAND = 98
 RC_BADCONFIG = 97
 
 
+def _subprocess_setup():
+    # Python installs a SIGPIPE handler by default. This is usually not what
+    # non-Python subprocesses expect.
+    signal.signal(signal.SIGPIPE, signal.SIG_DFL)
+
+
 if __name__ == '__main__':
     # Split arguments, require at least a command
     execname = sys.argv.pop(0)
@@ -84,6 +91,7 @@ if __name__ == '__main__':
                                stdin=sys.stdin,
                                stdout=sys.stdout,
                                stderr=sys.stderr,
+                               preexec_fn=_subprocess_setup,
                                env=filtermatch.get_environment(userargs))
         obj.wait()
         sys.exit(obj.returncode)

quantum/agent/linux/utils.py

@@ -21,6 +21,7 @@ import fcntl
 import logging
 import os
 import shlex
+import signal
 import socket
 import struct
 
@@ -30,6 +31,12 @@ from eventlet.green import subprocess
 LOG = logging.getLogger(__name__)
 
 
+def _subprocess_setup():
+    # Python installs a SIGPIPE handler by default. This is usually not what
+    # non-Python subprocesses expect.
+    signal.signal(signal.SIGPIPE, signal.SIG_DFL)
+
+
 def execute(cmd, root_helper=None, process_input=None, addl_env=None,
             check_exit_code=True, return_stderr=False):
     if root_helper:
@@ -42,6 +49,7 @@ def execute(cmd, root_helper=None, process_input=None, addl_env=None,
         env.update(addl_env)
     obj = subprocess.Popen(cmd, shell=False, stdin=subprocess.PIPE,
                            stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+                           preexec_fn=_subprocess_setup,
                            env=env)
 
     _stdout, _stderr = (process_input and

quantum/common/utils.py

@@ -23,6 +23,7 @@
 
 import logging
 import os
+import signal
 import subprocess
 import uuid
 
@@ -47,6 +48,12 @@ def boolize(subject):
     return subject
 
 
+def _subprocess_setup():
+    # Python installs a SIGPIPE handler by default. This is usually not what
+    # non-Python subprocesses expect.
+    signal.signal(signal.SIGPIPE, signal.SIG_DFL)
+
+
 def execute(cmd, process_input=None, addl_env=None, check_exit_code=True):
     logging.debug("Running cmd: %s", cmd)
     env = os.environ.copy()
@@ -54,6 +61,7 @@ def execute(cmd, process_input=None, addl_env=None, check_exit_code=True):
         env.update(addl_env)
     obj = subprocess.Popen(cmd, shell=True, stdin=subprocess.PIPE,
                            stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+                           preexec_fn=_subprocess_setup,
                            env=env)
     result = None
     if process_input is not None: