XL Fortran Enterprise Edition for AIX : User's Guide - IBM

!*****************************************************************
use, intrinsic::f_pthread
integer(4) ret_val
type(f_pthread_mutex_t) mutex
type(f_pthread_cond_t) cond
pointer(p, byte)
! Initialize mutex and condition variables before using them.
! For global variables this should be done in a module, so that they
! can be used by all threads. If they are local, other threads
! will not see them. Furthermore, they must be managed carefully
! (for example, destroy them before returning, to avoid dangling and
! undefined objects).
mutex = PTHREAD_MUTEX_INITIALIZER
cond = PTHREAD_COND_INITIALIZER
......
! Doing something
......
! This thread needs to allocate some memory area used to
! synchronize with other threads. However, when it waits on a
! condition variable, this thread may be canceled by another
! thread. The allocated memory may be lost if no measures are
! taken in advance. This will cause memory leakage.
ret_val = f_pthread_mutex_lock(mutex)
p = malloc(%val(4096))
! Check condition. If it is not true, wait for it.
! This should be a loop.
! Since memory has been allocated, cleanup must be registered
! for safety during condition waiting.
ret_val = f_pthread_cleanup_push(mycleanup, FLAG_DEFAULT, p)
ret_val = f_pthread_cond_wait(cond, mutex)
! If this thread returns from condition waiting, the cleanup
! should be de-registered.
call f_pthread_cleanup_pop(0) ! not execute
ret_val = f_pthread_mutex_unlock(mutex)
! This thread will take care of p for the rest of its life.
......
! mycleanup looks like:
subroutine mycleanup(passed_in)
pointer(passed_in, byte)
external free
call free(%val(passed_in))
end subroutine mycleanup
410 XL Fortran Enterprise Edition for AIX : User’s Guide