Bug #264435 - Handle EAGAIN errors when writing to stdout, due to poorly

behaved subprocesses that set O_NONBLOCK mode on inherited file descriptors.
TODO: When possible, avoid having child processes inherit stdio file
descriptors from portage (maybe it can't be avoided with
PROPERTIES=interactive). (trunk r13306)

svn path=/main/branches/2.1.6/; revision=13477

diff --git a/pym/_emerge/__init__.py b/pym/_emerge/__init__.py
index f0ece4e8cccadab842e44819449b74be63cedc39..d2031de10750aa91087326dc507a01bc64780ff7 100644 (file)
--- a/pym/_emerge/__init__.py
+++ b/pym/_emerge/__init__.py
@@ -2407,8 +2407,41 @@ class SpawnProcess(SubProcess):
 
                        if buf:
                                if not self.background:
-                                       buf.tofile(files.stdout)
-                                       files.stdout.flush()
+                                       write_successful = False
+                                       failures = 0
+                                       while True:
+                                               try:
+                                                       if not write_successful:
+                                                               buf.tofile(files.stdout)
+                                                               write_successful = True
+                                                       files.stdout.flush()
+                                                       break
+                                               except IOError, e:
+                                                       if e.errno != errno.EAGAIN:
+                                                               raise
+                                                       del e
+                                                       failures += 1
+                                                       if failures > 50:
+                                                               # Avoid a potentially infinite loop. In
+                                                               # most cases, the failure count is zero
+                                                               # and it's unlikely to exceed 1.
+                                                               raise
+
+                                                       # This means that a subprocess has put an inherited
+                                                       # stdio file descriptor (typically stdin) into
+                                                       # O_NONBLOCK mode. This is not acceptable (see bug
+                                                       # #264435), so revert it. We need to use a loop
+                                                       # here since there's a race condition due to
+                                                       # parallel processes being able to change the
+                                                       # flags on the inherited file descriptor.
+                                                       # TODO: When possible, avoid having child processes
+                                                       # inherit stdio file descriptors from portage
+                                                       # (maybe it can't be avoided with
+                                                       # PROPERTIES=interactive).
+                                                       fcntl.fcntl(files.stdout.fileno(), fcntl.F_SETFL,
+                                                               fcntl.fcntl(files.stdout.fileno(),
+                                                               fcntl.F_GETFL) ^ os.O_NONBLOCK)
+
                                buf.tofile(files.log)
                                files.log.flush()
                        else: