[Mono-dev] Anonymous Pipe Stream Implementation

SmokingRope smokingrope at gmail.com
Sun Jul 14 17:07:20 UTC 2013

Thanks for the feedback

I started this project merely as an investigation into whether it was even
possible to implement in unix, and so hadn't really thought far enough
ahead as to sharing it. The code is now pushed to a fork on github:

In terms of compatiblity i have not needed to change any existing dll
references. At this point i have added two internal calls to the
corlib\System.IO.MonoIO class. Perhaps you could look over these new
internal calls and give a little more specific advice on what (if anything)
needs conditioned out.
        I reused the poll() wrapper from the sockets implementation, (as
MonoIO.PollFD) so i assume that is ok.
        I am re-using the existing CreatePipe() function for pipe creation,
so that behaves the same as before.
        The GetPipeHandle() internal call just initializes a handle that
was inherited from a parent process in mono's file descriptor table, which
would not strike me as a compatibilty concern on it's own as it's only
doing mono platform work.

A new problem has presented itself, which some expert feedback would be
appreciated. Based on the sample code:

  1) Process.Start() is called on the server application to launch the
client application
  2) When the client application is started, it will inherit the pipe
handle and eventually start using it
  3) The server application calls DisposeLocalCopyOfClientHandle()
  4) The server writes to the pipe

   There is a synchronization issue between when 2 and 3 run, because in my
testing, sometimes the Process.Start() call has not fully completed
launching the child process, and closing the client handle on the server
side cause the pipe to be broken before the client is fully booted. Because
the pipe is broken step 4 should fail, though right now this isn't quite
happening :)

  With a Thread.Sleep(10) in DisposeLocalCopyOfClientHandle() the code
seems to work about 50% of the time on my machine. With no sleep, the pipe
seems to be broken every time.

  With the technical explanation out of the way, is there any way i could
wait / yield, and force the Process.Start() to complete launching the
client before DisploseLocalCopyOfClientHandle() complete? I can certainly
find some threshold where Thread.Sleep() reliably fixes the issue on my
machine, but it may not be nearly as reliable across platforms either, and
may need to be pretty huge (multiple seconds maybe?) to really get good
reliability that way.

I also would still appreciate some feedback on the handle inheritance

There aren't any tests yet, and i'm pretty severely violating the coding
standards document at this point, so both of those things are still on my
todo list. I'd also like to throw together the win32 implementation as well
(something that would be compatible with the MS.NET implementation).
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