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Sorry that this message is not a true reply to Corinna's reply. I was not yet actually subscribed to the mailing list when she sent her message, so I couldn't reply. Sorry also for not attaching the cygcheck.out file, which I have now done. I did put my Cygwin version in the subject of my message (1.7.7), as suggested in the reporting guidelines. Mark On Nov 17 11:20, Mark Rivers wrote: > Folks, > > I believe I have discovered a problem with blocking sockets on Cygwin. > The problem is that very rarely a call to send() will never return. > > I am having problem when using the Channel Access TCP/IP protocol in the > EPICS control system (http://www.aps.anl.gov/epics/). > > I have isolated the problem to a call to send() on the server which > never returns. This problem happens with a large number of well-tested > clients, running on both Linux and Windows. I can build the same EPICS > server without Cygwin, using the MS VC++ Windows compiler and libraries > and it does not fail. When the call to send() hangs it is sending a > large packet (just over 8KB). The failure rate is very low, perhaps > once in 10 million calls to send(). Wow, that's not very often. You missed all the stuff from http://cygwin.com/problems.html, so we don't know what Cygwin release you're talking about. If it's Cygwin 1.5, you're out of luck since we don't support that anymore. Otherwise... > I realize that my application is difficult to reproduce for the Cygwin > developers. I am willing to try to write a simple socket server and > client to try to reproduce the problem in a simple test setup. ...that would be most helpful. > But > before I do that I would like to first know if there is a known problem > of this sort that has already been reported, and perhaps fixed. No, not really. I wouldn't claim that Cygwin's socket implementation is bug free, but this kind of very occassional hang is new to me. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Project Co-Leader cygwin AT cygwin DOT com Red Hat -----Original Message----- From: Mark Rivers Sent: Wednesday, November 17, 2010 11:20 AM To: 'cygwin AT cygwin DOT com' Subject: 1.7.7 blocking socket problem Folks, I believe I have discovered a problem with blocking sockets on Cygwin. The problem is that very rarely a call to send() will never return. I am having problem when using the Channel Access TCP/IP protocol in the EPICS control system (http://www.aps.anl.gov/epics/). I have isolated the problem to a call to send() on the server which never returns. This problem happens with a large number of well-tested clients, running on both Linux and Windows. I can build the same EPICS server without Cygwin, using the MS VC++ Windows compiler and libraries and it does not fail. When the call to send() hangs it is sending a large packet (just over 8KB). The failure rate is very low, perhaps once in 10 million calls to send(). I realize that my application is difficult to reproduce for the Cygwin developers. I am willing to try to write a simple socket server and client to try to reproduce the problem in a simple test setup. But before I do that I would like to first know if there is a known problem of this sort that has already been reported, and perhaps fixed. I did look through the mailing list archives and did not see anything. This problem occurs on every Cygwin system it has been tested on (more than 6), so it is not restricted to particular hardware. All systems are running Windows XP SP3 I believe. Thanks very much, Mark Rivers
Attachment:
cygcheck.out
Description: cygcheck.out
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