[PATCH] Use C11 atomics instead atomic_decrement_and_test

[Wilco Dijkstra <Wilco.Dijkstra@arm.com>]

Replace atomic_decrement_and_test with atomic_fetch_add_relaxed.

Passes regress on AArch64.

---

diff --git a/htl/pt-dealloc.c b/htl/pt-dealloc.c
index c776e3471dc376977ca7058f0d143f0a842d5799..86bbb3091fbd3758b06294ca705dc774cf8bf0eb 100644
--- a/htl/pt-dealloc.c
+++ b/htl/pt-dealloc.c
@@ -33,7 +33,7 @@ extern pthread_mutex_t __pthread_free_threads_lock;
 void
 __pthread_dealloc (struct __pthread *pthread)
 {
-  if (!atomic_decrement_and_test (&pthread->nr_refs))
+  if (atomic_fetch_add_relaxed (&pthread->nr_refs, -1) != 1)
     return;
 
   /* Withdraw this thread from the thread ID lookup table.  */
diff --git a/htl/pt-exit.c b/htl/pt-exit.c
index f0759c8738e6da4c8e0ba47f6d15720203f6954e..3c0a8c52f34ed64b94ce71a0764512cb76351a3a 100644
--- a/htl/pt-exit.c
+++ b/htl/pt-exit.c
@@ -50,7 +50,7 @@ __pthread_exit (void *status)
 
   /* Decrease the number of threads.  We use an atomic operation to
      make sure that only the last thread calls `exit'.  */
-  if (atomic_decrement_and_test (&__pthread_total))
+  if (atomic_fetch_add_relaxed (&__pthread_total, -1) == 1)
     /* We are the last thread.  */
     exit (0);
 
diff --git a/manual/llio.texi b/manual/llio.texi
index 4e6e3fb672bb8ecbb1bb52faf3d70d9b7b33973f..eba9a0e6593f17116b41ff302cfca05846727155 100644
--- a/manual/llio.texi
+++ b/manual/llio.texi
@@ -2614,7 +2614,7 @@ aiocb64}, since the LFS transparently replaces the old interface.
 @c      free @ascuheap @acsmem
 @c     libc_thread_freeres
 @c      libc_thread_subfreeres ok
-@c     atomic_decrement_and_test ok
+@c     atomic_fetch_add_relaxed ok
 @c     td_eventword ok
 @c     td_eventmask ok
 @c     atomic_compare_exchange_bool_acq ok
diff --git a/nptl/cond-perf.c b/nptl/cond-perf.c
index 9c9488e2743f17eb4beeaadf45ef83a38a9f9bf9..baf69e6d34fdb3ffef97b32fb9db422077a0359b 100644
--- a/nptl/cond-perf.c
+++ b/nptl/cond-perf.c
@@ -24,7 +24,7 @@ cons (void *arg)
 
   do
     {
-      if (atomic_decrement_and_test (&ntogo))
+      if (atomic_fetch_add_relaxed (&ntogo, -1) == 1)
 	{
 	  pthread_mutex_lock (&mut2);
 	  alldone = true;
diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index 2602dba54e872f36bd54955af7587378e5dc3812..ada3fdd4d440c3fdcf4567734a452c8ba4d0fce1 100644
--- a/nptl/pthread_create.c
+++ b/nptl/pthread_create.c
@@ -489,7 +489,7 @@ start_thread (void *arg)
      the breakpoint reports TD_THR_RUN state rather than TD_THR_ZOMBIE.  */
   atomic_fetch_or_relaxed (&pd->cancelhandling, EXITING_BITMASK);
 
-  if (__glibc_unlikely (atomic_decrement_and_test (&__nptl_nthreads)))
+  if (__glibc_unlikely (atomic_fetch_add_relaxed (&__nptl_nthreads, -1) == 1))
     /* This was the last thread.  */
     exit (0);
 
diff --git a/sysdeps/nptl/libc_start_call_main.h b/sysdeps/nptl/libc_start_call_main.h
index a9e85f2b098dfc6790d719bba9662e428ab237e6..c10a16b2c4a61e74f6bf18396935b87208df4f7e 100644
--- a/sysdeps/nptl/libc_start_call_main.h
+++ b/sysdeps/nptl/libc_start_call_main.h
@@ -65,7 +65,7 @@ __libc_start_call_main (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
       /* One less thread.  Decrement the counter.  If it is zero we
          terminate the entire process.  */
       result = 0;
-      if (! atomic_decrement_and_test (&__nptl_nthreads))
+      if (atomic_fetch_add_relaxed (&__nptl_nthreads, -1) != 1)
         /* Not much left to do but to exit the thread, not the process.  */
 	while (1)
 	  INTERNAL_SYSCALL_CALL (exit, 0);