[Live-devel] A question about thread safety.

[Jeff Shanab]

I know live555 is an event model application and thread safety must be added if needed.

I pull and record from hundreds of cameras. Because of some OS limitaitions I can only wait on a maximum of 64 events.

So I have threads called processors for each group of 60 sources. Each of these has their own UsageEnvironment and TaskScheduler and event loop.

Is this a reliable architecture?

I do have an occasional access violation in Medium::~Medium() in units in the field, but today's problem is distinctly different.
It only occurs with one brand of camera.
    Am I correct in assuming no camera, no matter how bad the stream, should be able to crash live555?

The access violation always occurs in the same location.
 On the delete packet; line of

 ReorderingPacketBuffer::freePacket(BufferedPacket* packet){

    if (packet != fSavedPacket) {

      delete packet;

    } else {

      fSavedPacketFree = True;

    }

  }



In all inspections of memory the packet, whose pointer is not null, appears to already be destructed. The fBuf and vPtr are a special value 0xdddddddd which is Microsofts way of saying this memory was explicitly deleted.



The call stack always shows we are a few frames down from MultiFramedRTPSource::networkReadHandler1() and I was trying to figure it out.

I came across a question. Given the implementation of bytesAvailable() should the line "if bPacket->bytesavailable() == 0)..." be if bPacket->bytesavailable() <= 0)..."



I am looking for suggestions on where to look for the source of this problem. Simple or scaled down examples do not have a problem. Valgrind like tools on windows have a high overhead and also seem to effect the occurrence. (Indicates a race!)



Thanks


   Jeff Shanab, Manager-Software Engineering
   D 630.633.4515 | C 630.453.7764 | F 630.633.4815 | jshanab at smartwire.com<mailto:jshanab at smartwire.com>
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