title: Is msgsnd() thread- and/or process-safe?
body: <p>What happens if two pthreads are calling the msgsnd() function at the "same" time, posting message to the same message queue ?</p>
  
  <p>What if two processes do the same ? Does it matter if they are threads or processes ?</p>
  
  <p>Specifically interested for Linux 2.6.15-2.5 #1 SMP PREEMPT Tue Sep 19 10:56:25 CDT 2006 x86_64 x86_64 x86_64 GNU/Linux</p>