[ace-users] Acceptor pattern w/ select reactor notification crash...

Douglas C. Schmidt schmidt at dre.vanderbilt.edu
Fri Sep 28 11:11:40 CDT 2007

Hi Mark,

Thanks for using the PRF.

>ACE 5.5.8
>Fedora core 5 linux
>Acceptor  pattern
>Selector reactor
>Notification strategy
>I am getting quite a few segmentation faults that appear in the 
>following manner.
>A client connects to the acceptor and begins sending and receiving messages.
>After some point the client disconnects - either expected (logoff) or 
>unexpected (dropped network).
>I catch the SIGPIPE signal and enqueue a HANGUP message as follows:
>    a) Note the current notification strategy
>    b) NULL the notification strategy
>    c) Construct an ACE_Message_Block with length 0 and message type set 
>    d) Put above message on message queue.
>    e) If cached notification strategy from step a is not NULL then call 
>notify on it.
>    f) Return 0
>I run the app and see that someone is putting a message on my  message 
>queue and triggering
>my notification strategy to push my object back on the reactors 
>notification pipe. Then when
>I'm reading my message_queue in handle_output I find the message with 
>the message type of
>MB_HANGUP and return -1 (which is my understanding will call 
>handle_close which in turn
>deletes the object). Then the reactor notification pipe attempts to call 
>this object to handle_output
>again and crashes since the object has been freed inside the 
>handle_close method.
>So, the question is what is the correct way to close an ACE_Svc_Handler 
>when a SIGPIPE occurs?

There are some examples of this sort of thing in Chapters 6 and 7 of
C++NPv2 <www.cs.wustl.edu/~schmidt/ACE/book2/>.  I recommend you take
a look there and see if they shed any light on what you're doing.


Dr. Douglas C. Schmidt                       Professor and Associate Chair
Electrical Engineering and Computer Science  TEL: (615) 343-8197
Vanderbilt University                        WEB: www.dre.vanderbilt.edu/~schmidt
Nashville, TN 37203                          NET: d.schmidt at vanderbilt.edu

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