[zeromq-dev] zmq-signaler-port-sync

Pau pau at teleopsia.com
Wed Feb 13 08:28:55 CET 2013


Hi,

I am back with the asserts happening inside a critical section in 
signaler.cpp.
The problem still is that in signale.cpp make_fdpair(..) creates 
system-wide critical section and does a number of things that can 
generate a wsa_assert() or win_assert() before releasing the session.

I have seen that in the trunk someone has added a CloseHandle(sync) at 
the end of the function, I do not know if it had something related with 
this but I understand that the problem is still there. wsa_assert() and 
wsa_windows() end up in RaiseException (0x40000015, 
EXCEPTION_NONCONTINUABLE, 1, extra_info) which I understand is a cul de 
sac that has no way out to clean up before leaving.

I guess we need a special assert function to use inside this critical 
but I'd like a more documented opinion (Kiu?).

thanks,

Pau Ceano

El 21/01/2013 23:37, KIU Shueng Chuan escribió:
>
> Hi Pau, a fix for the assertion on connection to port 5905 is in trunk 
> branch.
>
> I think the dangling critical section possibility could be fixed by 
> changing the Event to a Mutex. When an assertion occurs the mutex 
> would just be abandoned. However this change will cause backward 
> compatibility issues with older versions.
>
> On Jan 22, 2013 2:04 AM, "Pieter Hintjens" <ph at imatix.com 
> <mailto:ph at imatix.com>> wrote:
>
>     Hi Pau,
>
>     So there are two different problems here, one is that we're hitting a
>     socket limit on WXP, and the other is that the asserts are happening
>     inside a critical section.
>
>     I don't think we can fix the first one easily but we can presumably
>     assert in a smarter way. Do you want to try making a patch for this?
>
>     -Pieter
>
>     On Mon, Jan 21, 2013 at 6:23 PM, Pau <pau at teleopsia.com
>     <mailto:pau at teleopsia.com>> wrote:
>     >
>     > Hi,
>     >
>     >
>     > I am using (not yet in production) ZMQ on Windows and I have
>     found what
>     > I think is a big problem for Windows users.
>     > We use WXP and W7 and Visual C++ different versions. ZMQ version
>     3.2.0
>     > (as far as I see the same problem happens in 3.2.2)
>     >
>     > I do not fully understand ZMQ internals but I've seen that every
>     time a
>     > socket is created the function make_fdpair(..) is called and in
>     > signaler.cpp(line244) a system event "zmq-signaler-port-sync" is
>     created.
>     > This event is used as a system-wide critical section and, so all
>     > applications that try to create an event will
>     WaitForSingleObject (sync,
>     > INFINITE) until  SetEvent (...) is called.
>     > The problem is that the code between:
>     >   HANDLE sync = CreateEvent (NULL, FALSE, TRUE, TEXT
>     > ("zmq-signaler-port-sync"));
>     > and
>     > SetEvent (sync);
>     > is full of wsa_asserts(..) that will terminate the application if
>     > something goes wrong.
>     >
>     > It is clear that terminating the application not leaving the
>     system-wide
>     > critical section is a bad idea because all applications in the
>     system
>     > will hang and you will have to stop all them to start again.
>     > I understand that no errors should happen but anyway to escape
>     from the
>     > error is not a good idea in this case.
>     >
>     > I do not know all possible reasons to generate a fatal
>     wsa_assert(..)
>     > but there is at least one:
>     >
>     > I have seen that in XP it is possible that line 301  rc =
>     connect (*w_,
>     > (sockaddr *) &addr, sizeof (addr)); returns an error when a
>     socket tries
>     > to connect to 5905 and this has happened many times.
>     > Windows uses port numbers starting near 1400 and XP has a limit
>     at 5000.
>     > In W7 this does not look as a problem because maximum is 65000
>     > It sounds as if the number was big enough but apart from the
>     fact that
>     > ZMQ uses a big number of connections (at least in my tests) I have
>     > experienced that Windows jumps port numbers by 7, so 5000 happens
>     > sometimes with catastrophic consequences.
>     >
>     > best,
>     >
>     > Pau Ceano
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