[Mono-dev] _wapi_connect stuck in poll()

yoni shalom silver83 at gmail.com
Tue May 25 15:05:11 EDT 2010

Tested on Mono, 2.6.x
Both leopard and snow leopard.

It seems as though _sometime_ (ranges from 0 to 5 out of 50) threads
that are in the middle of performing Socket.Connect() on which
Thread.Abort() is called, never exit and cause the thread to "leak"
and be stuck indefinitely.

The offending thread is stuck in
I'm attaching a test program - just let it run, wait for 30 seconds
and then in gdb display all stacks ( t apply all bt ) and you will see
the threads stuck in ves_blabla_Connect_Internal()

The code I'm talking about is this (mono/io-layer/sockets.c) :

while (poll (&fds, 1, -1) ==  -1 &&
           !_wapi_thread_cur_apc_pending ()) {
      if (errno != EINTR) {
        errnum = errno_to_WSA (errno, __func__);

#ifdef DEBUG
        g_message ("%s: connect poll error: %s",
             __func__, strerror (errno));

        WSASetLastError (errnum);

I've been trying to debug this code without much luck understanding
what is special to the misbehaving scenario...

A change in the first line of code, allowing for a timeout of 3
seconds in the poll syscall (not sure how correct this is), seems to
solve the problem for me.
int prslt;
while(((prslt = poll(&fds, 1, 3000)) == 0) || (prslt == -1 &&
         !_wapi_thread_cur_apc_pending()) {

Obviously this is not optimal, and as such - is not a solution
proposal but just additional info.
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