Hello everyone,
Please read the attached emails.
I would like to understand exactly what broke twisted, so that we're
sure the new 2.6.11 kernel will work reliably with twisted.
This code especially will never trigger with 2.6.11 because we'll never
set POLLIN|POLLOUT at the same time for writeable fd.
def doRead(self):
"""The only way this pipe can become readable is at EOF, because the
child has closed it.
"""
fd = self.fd
r, w, x = select.select([fd], [fd], [], 0)
if r and w:
return CONNECTION_LOST
Could you answer why anybody should call doRead on a writeable fd?
Where is it written that at EOF a _write_ pipe channel becomes readable?
Is it ok that "r and w" will never trigger at the same time anymore,
right? Was just that a superflous assumptions?
Note that with 2.6.8 and all previous linux kernels, "r and w" could be
== True in normal conditions too if the pipe write buffer was empty (old
kernel was setting pollin always for no good reason).
What I suspect is that the above is a superflous check that was working
by luck with older kernels (becasue we could set in and out at the same
time even without a disconnect event), and that all you care about is to
get the wakeup from the write or disconnect events. And in turn the new
linux 2.6.11-rc should not work by luck anymore.
Comments appreciated.
Thanks.
