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SubjectRe: Strange intermittent EIO error when writing to stdout since v3.8.0
On 06/06/2013 07:54 AM, Markus Trippelsdorf wrote:
> Since v3.8.0 several people reported intermittent IO errors that happen
> during high system load while using "emerge" under Gentoo:
> ...
> File "/usr/lib64/portage/pym/portage/util/_eventloop/EventLoop.py", line 260, in iteration
> if not x.callback(f, event, *x.args):
> File "/usr/lib64/portage/pym/portage/util/_async/PipeLogger.py", line 99, in _output_handler
> stdout_buf[os.write(stdout_fd, stdout_buf):]
> File "/usr/lib64/portage/pym/portage/__init__.py", line 246, in __call__
> rval = self._func(*wrapped_args, **wrapped_kwargs)
> OSError: [Errno 5] Input/output error

Looks to me like a user-space bug: EIO is returned when the other
end of the "pipe" has been closed.

FWIW, I didn't see where the OP tried to revert
'SpawnProcess: stdout_fd FD_CLOEXEC'

The only non-emerge related comment (#21 in the link provided) refers to
'a similar issue sometimes happened when I built Firefox by hand [..snip..]
And it would randomly crash during the build.

Since I've recompiled Python with gcc-4.6 this issue also never occurred
again.'

That comment doesn't really corroborate the reported bug.

Regards,
Peter Hurley

> Basically 'emerge' just writes the build output to stdout in a loop:
> ...
> def _output_handler(self, fd, event):
>
> background = self.background
> stdout_fd = self.stdout_fd
> log_file = self._log_file
>
> while True:
> buf = self._read_buf(fd, event)
>
> if buf is None:
> # not a POLLIN event, EAGAIN, etc...
> break
>
> if not buf:
> # EOF
> self._unregister()
> self.wait()
> break
>
> else:
> if not background and stdout_fd is not None:
> failures = 0
> stdout_buf = buf
> while stdout_buf:
> try:
> stdout_buf = \
> stdout_buf[os.write(stdout_fd, stdout_buf):]
> except OSError as e:
> if e.errno != errno.EAGAIN:
> raise
> ...
>
> see: https://bugs.gentoo.org/show_bug.cgi?id=459674
>
> (A similar issue also happens when building Firefox since v3.8.0. But
> because Firefox's build process doesn't raise an exception it just dies
> at random points without giving a clue.)
>
> Now the question is: Could this be a kernel bug? Maybe in the TTY layer?
>
> Unfortunately the issue is not easily reproducible and a git-bisect is
> out of the question.
>



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