bpo-30805: Avoid race condition with debug logging (GH-7545)

Supersedes #2490
(cherry picked from commit 12f482e)

Co-authored-by: Yury Selivanov <[email protected]>

Author: miss-islington

Lib/asyncio/base_events.py

@@ -1153,14 +1153,15 @@ def subprocess_shell(self, protocol_factory, cmd, *, stdin=subprocess.PIPE,
         if bufsize != 0:
             raise ValueError("bufsize must be 0")
         protocol = protocol_factory()
+        debug_log = None
         if self._debug:
             # don't log parameters: they may contain sensitive information
             # (password) and may be too long
             debug_log = 'run shell command %r' % cmd
             self._log_subprocess(debug_log, stdin, stdout, stderr)
         transport = yield from self._make_subprocess_transport(
             protocol, cmd, True, stdin, stdout, stderr, bufsize, **kwargs)
-        if self._debug:
+        if self._debug and debug_log is not None:
             logger.info('%s: %r', debug_log, transport)
         return transport, protocol
 
@@ -1182,6 +1183,7 @@ def subprocess_exec(self, protocol_factory, program, *args,
                                 "a bytes or text string, not %s"
                                 % type(arg).__name__)
         protocol = protocol_factory()
+        debug_log = None
         if self._debug:
             # don't log parameters: they may contain sensitive information
             # (password) and may be too long
@@ -1190,7 +1192,7 @@ def subprocess_exec(self, protocol_factory, program, *args,
         transport = yield from self._make_subprocess_transport(
             protocol, popen_args, False, stdin, stdout, stderr,
             bufsize, **kwargs)
-        if self._debug:
+        if self._debug and debug_log is not None:
             logger.info('%s: %r', debug_log, transport)
         return transport, protocol
 

Misc/NEWS.d/next/Library/2018-06-08-17-34-16.bpo-30805.3qCWa0.rst

@@ -0,0 +1 @@
+Avoid race condition with debug logging