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BUG: Ensure that kernel can be spawned from a backgrounded process.

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1 parent 56d2d8d commit adba85c00016d40383a5991854916c63b2ecc03f epatters committed Aug 19, 2011
Showing with 34 additions and 25 deletions.
  1. +34 −25 IPython/zmq/entry_point.py
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@@ -85,30 +85,37 @@ def base_launch_kernel(code, shell_port=0, iopub_port=0, stdin_port=0, hb_port=0
executable = sys.executable
arguments = [ executable, '-c', code, '--shell=%i'%shell_port,
'--iopub=%i'%iopub_port, '--stdin=%i'%stdin_port,
- '--hb=%i'%hb_port
- ]
+ '--hb=%i'%hb_port ]
if ip is not None:
arguments.append('--ip=%s'%ip)
arguments.extend(extra_arguments)
+ # Popen will fail (sometimes with a deadlock) if stdin, stdout, and stderr
+ # are invalid. Unfortunately, there is in general no way to detect whether
+ # they are valid. The following two blocks redirect them to (temporary)
+ # pipes in certain important cases.
+
+ # If this process has been backgrounded, our stdin is invalid. Since there
+ # is no compelling reason for the kernel to inherit our stdin anyway, we'll
+ # place this one safe and always redirect.
+ redirect_in = True
+ _stdin = PIPE if stdin is None else stdin
+
+ # If this process in running on pythonw, we know that stdin, stdout, and
+ # stderr are all invalid.
+ redirect_out = sys.executable.endswith('pythonw.exe')
+ if redirect_out:
+ _stdout = PIPE if stdout is None else stdout
+ _stderr = PIPE if stderr is None else stderr
+ else:
+ _stdout, _stderr = stdout, stderr
+
# Spawn a kernel.
if sys.platform == 'win32':
# Create a Win32 event for interrupting the kernel.
interrupt_event = ParentPollerWindows.create_interrupt_event()
arguments += [ '--interrupt=%i'%interrupt_event ]
- # If this process in running on pythonw, stdin, stdout, and stderr are
- # invalid. Popen will fail unless they are suitably redirected. We don't
- # read from the pipes, but they must exist.
- if sys.executable.endswith('pythonw.exe'):
- redirect = True
- _stdin = PIPE if stdin is None else stdin
- _stdout = PIPE if stdout is None else stdout
- _stderr = PIPE if stderr is None else stderr
- else:
- redirect = False
- _stdin, _stdout, _stderr = stdin, stdout, stderr
-
# If the kernel is running on pythonw and stdout/stderr are not been
# re-directed, it will crash when more than 4KB of data is written to
# stdout or stderr. This is a bug that has been with Python for a very
@@ -139,20 +146,22 @@ def base_launch_kernel(code, shell_port=0, iopub_port=0, stdin_port=0, hb_port=0
# Attach the interrupt event to the Popen objet so it can be used later.
proc.win32_interrupt_event = interrupt_event
- # Clean up pipes created to work around Popen bug.
- if redirect:
- if stdin is None:
- proc.stdin.close()
- if stdout is None:
- proc.stdout.close()
- if stderr is None:
- proc.stderr.close()
-
else:
if independent:
proc = Popen(arguments, preexec_fn=lambda: os.setsid(),
- stdin=stdin, stdout=stdout, stderr=stderr)
+ stdin=_stdin, stdout=_stdout, stderr=_stderr)
else:
proc = Popen(arguments + ['--parent=1'],
- stdin=stdin, stdout=stdout, stderr=stderr)
+ stdin=_stdin, stdout=_stdout, stderr=_stderr)
+
+ # Clean up pipes created to work around Popen bug.
+ if redirect_in:
+ if stdin is None:
+ proc.stdin.close()
+ if redirect_out:
+ if stdout is None:
+ proc.stdout.close()
+ if stderr is None:
+ proc.stderr.close()
+
return proc, shell_port, iopub_port, stdin_port, hb_port

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