We are continuing our long drawn out effort to port the SIMPL toolkit (http://www.icanprogram.com/simpl) to the Cygwin platform. For a long time we were unable to proceed due to issues with the fifo implementation under Cygwin. These issues have largely been addressed in more recent Cygwin releases. However, some curious and frustrating issues remain.
The most difficult remaining issue concerns the difference in blocking behavior of Cygwin RDWR fifos versus their Linux counterparts. Under Linux you can open a fifo as RDWR and have it safely and conveniently block on the subsequent read if there is no information on the fifo (or no other partner on the other end). Under Cygwin RDWR fifos block on the open call until the partner shows up. We hacked around this "problem" by opening RDWR+O_NONBLOCK on Cygwin and then surrounding our reads with a selec()t on the file descriptor. While this hack works the performance under Cygwin is orders of magnitude slower than the equivalent Linux performance. Any suggestions on how we can achieve a higher performance blocking read on a Cygwin RDWR fifo? The second issue is related. The other end of these RDWR fifos is typically open WRONLY. Most of the time the open does not block but occasionally we have found a condition where this open does block. Early experimentation points to a condition whereby the fifo was previously opened and written to by another process and where that process continues to have an open file descriptor. Once again are there any good suggestions on how to avoid blocking on a multiplexed WRONLY fifo open? The final issue concerns the select() hack described above. When running our benchmark test which repeatly composes and sends a message, we notice that occasionally (once every 50 times or so) the select releases but the subsequent read fails with errno 11 (resource temporarily unavailable). If this error is "ignored" and the read retried things seem to work. Any ideas? Thanks in advance for your help. bob -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
