Using posix calls in rotor code

Hi,
 Can we use Posix calls for thread synchronization in rotor code? because
almost all calls used are the ones that are defined in /pal/unix
directory. and crucial functions such as suspendEE, restartEE assume that
all the threads are objects of 'class Thread'.
 to be more specific, if we introduce pthread mutexes/semaphores in the
code, what precautions should one take to ensure that the gc thread is
successful in suspending all the threads?

Thanks & regards
archana