> >> Hi Ken > >> > >>>>>>>>>>> Using AF_UNIX/SOCK_DGRAM with current version (3.2.0) > seems > >>> to > >>>>>>>>>>> drop messages or at least they are not received in the same > >>>>>>>>>>> order they are sent > >>>>>>> > >>>>>>> [snip] > >>>>>>> > >>>>>>>> Thanks for the test case. I can confirm the problem. I'm not > >>>>>>>> familiar enough with the current AF_UNIX implementation to > >>>>>>>> debug this easily. I'd rather spend my time on the new > >>>>>>>> implementation (on the topic/af_unix branch). It turns out > >>>>>>>> that your test case fails there too, but in a completely > >>>>>>>> different way, due to a bug in sendto for datagrams. I'll see > >>>>>>>> if I can fix that bug and then try again. > >>>>>>>> > >>>>>>>> Ken > >>>>>>> > >>>>>>> Ok, too bad it wasn't our own code base but good that the > "mystery" > >>>>>>> is verified > >>>>>>> > >>>>>>> I finally succeed to build topic/af_unix (after finding out what > >>>>>>> version of zlib was needed), but not with -D__WITH_AF_UNIX to > >>>>>>> CXXFLAGS though and thus I haven’t tested it yet > >>>>>>> > >>>>>>> Is it sufficient to add the define to the "main" Makefile or do > >>>>>>> you have to add it to all the Makefile:s ? I guess I can find > >>>>>>> out though > >>>>>> > >>>>>> I do it on the configure line, like this: > >>>>>> > >>>>>> ../af_unix/configure CXXFLAGS="-g -O0 -D__WITH_AF_UNIX" -- > >>> prefix=... > >>>>>> > >>>>>>> Is topic/af_unix fairly up to date with master branch ? > >>>>>> > >>>>>> Yes, I periodically cherry-pick commits from master to topic/af_unix. > >>>>>> I'lldo that again right now. > >>>>>> > >>>>>>> Either way, I'll be glad to help out testing topic/af_unix > >>>>>> > >>>>>> Thanks! > >>>>> > >>>>> I've now pushed a fix for that sendto bug, and your test case runs > >>>>> without error on the topic/af_unix branch. > >>>> > >>>> It seems like the test-case do work now with topic/af_unix in > >>>> blocking mode, but when using non-blocking (with MSG_DONTWAIT) > >>>> there are > >>> some > >>>> issues I think > >>>> > >>>> 1. When the queue is empty with non-blocking recv(), errno is set > >>>> to EPIPE but I think it should be EAGAIN (or maybe the pipe is > >>>> getting broken for real of some reason ?) > >>>> > >>>> 2. When using non-blocking recv() and no message is written at all, > >>>> it seems like recv() blocks forever > >>>> > >>>> 3. Using non-blocking recv() where the "client" does send less than > >>>> "count" messages, sometimes recv() blocks forever (as well) > >>>> > >>>> > >>>> My naïve analysis of this is that for the first issue (if any) the > >>>> wrong errno is set and for the second issue it blocks if no > >>>> sendto() is done after the first recv(), i.e. nothing kicks the "reader > thread" > >>>> in the butt to realise the queue is empty. It is not super clear > >>>> though what POSIX says about creating blocking descriptors and then > >>>> using non-blocking-flags with recv(), but this works in Linux any > >>>> way > >>> > >>> The explanation is actually much simpler. In the recv code where a > >>> bound datagram socket waits for a remote socket to connect to the > >>> pipe, I simply forget to handle MSG_DONTWAIT. I've pushed a > fix. Please retest. > >>> > >>> I should add that in all my work so far on the topic/af_unix branch, > >>> I've thought mainly about stream sockets. So there may still be > >>> things remaining to be implemented for the datagram case. > >> > >> I finally got some time to test topic/af_unix in our "real" > >> cygwin-application > >> (casual) and unfortunately very few of our unittests pass > >> > >> The symptoms are that there's unexpected eternal blocking, sometimes > >> there's unexpected EADDRNOTAVAIL, sometimes it looks like some > memory > >> corruption (and > >> core-dumps) > >> > >> Of course the memory corruption etc could be our self and the > >> core-dumps might be because of uncaught exceptions > >> > >> Needles to say is that all unittests pass on Linux, but of course > >> cygwin-topic/af_unix could act according to POSIX-standard and the > >> behaviour couldbe due to our own misinterpretation of how POSIX works > > > > More likely it's due to bugs in the topic/af_unix branch. This is > > still very much a work in progress. > > > >> I will try to narrow down the quite complex logic and reproduce the > >> problems > > > > That would be ideal. > > > >> If you of some reason wanna try it with casual, I'd be glad to help > >> you out (it should be easier now that last time (but there might be > >> some documentation missing for Cygwin still)) > >> > >> https://bitbucket.org/casualcore/ > > > > I'm going on vacation in a few days, but I might do this when I get back. > > > > Thanks for your testing. > > By the way, if your code is using datagram sockets, then there are very > serious > problems with our implementation (even aside from the performance issue > that we've already discussed). For example, I don't know of any reasonable > way for select to test whether such a socket is ready for writing. We'll > need to > solve that somehow.
If you by that mean if we're using SOCK_DGRAM, the answer is yes I tried SOCK_STREAM (and SOCK_SEQPACKET I think) for CYGWIN 3.2.0 but that didn't work at all As far as I understand, both all types on pretty much all implementations preserves message ordering though I haven't tried SOCK_STREAM and/or SOCK_SEQPACKET with the topic/af_unix-branch. Is that worth a try ? Best regards, Kristian > Ken -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
