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From: "Aylin Kantarci" <kantarci@bornova.ege.edu.tr>
To: <freebsd-realtime@freebsd.org>
Date: Fri, 13 Feb 2004 17:59:56 +0200
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Subject: A question on pthreads
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X-List-Received-Date: Fri, 13 Feb 2004 15:48:21 -0000

Now I have a question about my multithreaded application. I will be very
glad if you could be helpful.
 
I am developing the software on Solaris 9 platform and using pthread and
posix4 libraries.
 
There are 3 threads in the application and a periodic realtime thread.
 
The 1st thread receives packets from the network at small intervals.
 
The second thread catches signals from the periodic timer.
 
the 3rd thread consumes a group of packets at each clock tick.
 
The second and the third thread synchronizes with a mutex. 2nd thread
unlocks the mutex when the clock ticks.
the third thread tries to lock the mutex and consumes the packets in a
loop
 
All threads arse defined with the scope SYSTEM_SCOPE. I am setting the
thread concurrency to 5. I think I am using bounded threads.
 
I observed that when the 2nd thread tries to lock the mutex, the 1st
thread also blocks and stops receiving packets from the network. The 1st
thread uses an implementation of RTP library which is not thread safe.
 
I want the first thread to continue to receive packets from the network
when the second thread blocks on the semaphore.
 
Algorthm for the first thread
 
while (1)
 {
receive a packet from the network
.
.
.
_}
 
Algorithm for the 2nd one
 
.
.
.{
while (1)
{
.
.
 pthread mutex lock(cont)
consume packets
.
.
}
 
Algorithm for the 3rd one
{
 
while (1)
{
 
wait for a signal to arrive when the periodic timer ticks.
pthread mutex unlock( cont)
}
 
 
Thanks in advance
 
Dr. Aylin Kantarci