Hi there.
I have two threads. The main thread sends snmp requests, the other receives
responses. And I can only use snmp_sess_*() calls since it is
multithreaded.
I want to be able to send requests and forget about them until a response is
detected on the socket. I want to do this so that I don't have to wait on
responses as they could take a long time (might get timeout). This will
slow things down considerably. Hence, that's why the receive thread will
block on select() waiting for responses.
In the main thread, I send the requests using snmp_sess_async_send(), where
the callback function will be called in the receive thread after
snmp_sess_read() is called (also in the receive thread).
Basically, when I add a new snmp session (which are created for every snmp
request) I get the session's socket fd and update a global fd_set so that
the receive thread can call select() on it. I also use a pipe to wake up
the receive thread and tell it to call select() again on the updated
fd_set. Once the receive thread gets a response, I call snmp_sess_read() on
the corresponding session which calls the callback function.
I am using opaque pointers for sessions and only using snmp_sess_*() calls
as per README.threads recommendation. However, I am getting segmentation
faults when running my progam. It segfaults in the same place every time,
which is _sess_read which is called by snmp_sess_read(). I am guessing both
threads are trying to access the same data or something?
One thing I noticed is that if I don't clean up the sessions with
snmp_sess_close() then I do not get a segault. But obviously this is not
good since I get "Too many open files" error as I'm not clearing the
sessions. Hopefully this is a clue for someone.
I thought maybe cleaning up the sessions in the receive thread as opposed to
the main thread might have been the problem. So I tried cleaning any old
sessions lying about in the main thread instead. Didn't work, same
outcome. Seg fault on _sess_read().
Anyway, here is the pertinent code - http://pastebin.com/5SAke4FA
Hopefully you can see what I am trying to do. I would really appreciate any
help on this.
Thanks,
T
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