[zeromq-dev] missing events ZMQ_FD / ZMQ_EVENTS

Gerhard Lipp gelipp at googlemail.com
Mon May 14 18:49:41 CEST 2012

Hello Paul,

thanks for the diagram! I would like to locate the variables cntA  /
cntB in source to understand what is going on (and why). Could you
please point me in the right direction?


On Wed, May 2, 2012 at 12:27 PM, Paul Colomiets <paul at colomiets.name> wrote:
> Hi Gerhard,
> On Wed, May 2, 2012 at 12:45 PM, Gerhard Lipp <gelipp at googlemail.com> wrote:
>> I really appreciate any help and ideas to solve this issue! I just did
>> not get the idea behind this attempt.
>> Could you explain it in more detail (something particular to observe)?
> Ok. Behind the scenes ZMQ_FD, is basically a counter, which wakes up
> poll when is non-zero. The counter is reset on each getsockopt ZMQ_EVENTS,
> zmq_send and zmq_recv.
> The following diagram shows race condition with two sockets A and B,
> in a scenario similar to yours:
> https://docs.google.com/drawings/d/1F97jpdbYMjjb6-2VzRtiL2LpHy638-AEOyrUX84HL78/edit
> Note: the last poll is entered with both counters set to zero, so it
> will not wake up, despite the fact that there is pending message.
> --
> Paul
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