This patch fixes performance problems on multi-core machines
as reported at <https://bugs.gnu.org/26441>.

See commit 1afbcb06fded2a427b761dd1615b1e48e1e853cc in Gettext
by Bruno Haible <bruno@clisp.org>.

diff --git a/gettext-runtime/tests/test-lock.c b/gettext-runtime/tests/test-lock.c
index d279d1d60..51cec3d6b 100644
--- a/gettext-runtime/tests/test-lock.c
+++ b/gettext-runtime/tests/test-lock.c
@@ -1,5 +1,5 @@
 /* Test of locking in multithreaded situations.
-   Copyright (C) 2005, 2008-2016 Free Software Foundation, Inc.
+   Copyright (C) 2005, 2008-2017 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
@@ -50,6 +50,13 @@
    Uncomment this to see if the operating system has a fair scheduler.  */
 #define EXPLICIT_YIELD 1
 
+/* Whether to use 'volatile' on some variables that communicate information
+   between threads.  If set to 0, a lock is used to protect these variables.
+   If set to 1, 'volatile' is used; this is theoretically equivalent but can
+   lead to much slower execution (e.g. 30x slower total run time on a 40-core
+   machine.  */
+#define USE_VOLATILE 0
+
 /* Whether to print debugging messages.  */
 #define ENABLE_DEBUGGING 0
 
@@ -214,6 +221,51 @@ static inline void * gl_thread_self_pointer (void)
 # define yield()
 #endif
 
+#if USE_VOLATILE
+struct atomic_int {
+  volatile int value;
+};
+static void
+init_atomic_int (struct atomic_int *ai)
+{
+}
+static int
+get_atomic_int_value (struct atomic_int *ai)
+{
+  return ai->value;
+}
+static void
+set_atomic_int_value (struct atomic_int *ai, int new_value)
+{
+  ai->value = new_value;
+}
+#else
+struct atomic_int {
+  gl_lock_define (, lock)
+  int value;
+};
+static void
+init_atomic_int (struct atomic_int *ai)
+{
+  gl_lock_init (ai->lock);
+}
+static int
+get_atomic_int_value (struct atomic_int *ai)
+{
+  gl_lock_lock (ai->lock);
+  int ret = ai->value;
+  gl_lock_unlock (ai->lock);
+  return ret;
+}
+static void
+set_atomic_int_value (struct atomic_int *ai, int new_value)
+{
+  gl_lock_lock (ai->lock);
+  ai->value = new_value;
+  gl_lock_unlock (ai->lock);
+}
+#endif
+
 #define ACCOUNT_COUNT 4
 
 static int account[ACCOUNT_COUNT];
@@ -281,12 +333,12 @@ lock_mutator_thread (void *arg)
   return NULL;
 }
 
-static volatile int lock_checker_done;
+static struct atomic_int lock_checker_done;
 
 static void *
 lock_checker_thread (void *arg)
 {
-  while (!lock_checker_done)
+  while (get_atomic_int_value (&lock_checker_done) == 0)
     {
       dbgprintf ("Checker %p before check lock\n", gl_thread_self_pointer ());
       gl_lock_lock (my_lock);
@@ -311,7 +363,8 @@ test_lock (void)
   /* Initialization.  */
   for (i = 0; i < ACCOUNT_COUNT; i++)
     account[i] = 1000;
-  lock_checker_done = 0;
+  init_atomic_int (&lock_checker_done);
+  set_atomic_int_value (&lock_checker_done, 0);
 
   /* Spawn the threads.  */
   checkerthread = gl_thread_create (lock_checker_thread, NULL);
@@ -321,7 +374,7 @@ test_lock (void)
   /* Wait for the threads to terminate.  */
   for (i = 0; i < THREAD_COUNT; i++)
     gl_thread_join (threads[i], NULL);
-  lock_checker_done = 1;
+  set_atomic_int_value (&lock_checker_done, 1);
   gl_thread_join (checkerthread, NULL);
   check_accounts ();
 }
@@ -365,12 +418,12 @@ rwlock_mutator_thread (void *arg)
   return NULL;
 }
 
-static volatile int rwlock_checker_done;
+static struct atomic_int rwlock_checker_done;
 
 static void *
 rwlock_checker_thread (void *arg)
 {
-  while (!rwlock_checker_done)
+  while (get_atomic_int_value (&rwlock_checker_done) == 0)
     {
       dbgprintf ("Checker %p before check rdlock\n", gl_thread_self_pointer ());
       gl_rwlock_rdlock (my_rwlock);
@@ -395,7 +448,8 @@ test_rwlock (void)
   /* Initialization.  */
   for (i = 0; i < ACCOUNT_COUNT; i++)
     account[i] = 1000;
-  rwlock_checker_done = 0;
+  init_atomic_int (&rwlock_checker_done);
+  set_atomic_int_value (&rwlock_checker_done, 0);
 
   /* Spawn the threads.  */
   for (i = 0; i < THREAD_COUNT; i++)
@@ -406,7 +460,7 @@ test_rwlock (void)
   /* Wait for the threads to terminate.  */
   for (i = 0; i < THREAD_COUNT; i++)
     gl_thread_join (threads[i], NULL);
-  rwlock_checker_done = 1;
+  set_atomic_int_value (&rwlock_checker_done, 1);
   for (i = 0; i < THREAD_COUNT; i++)
     gl_thread_join (checkerthreads[i], NULL);
   check_accounts ();
@@ -467,12 +521,12 @@ reclock_mutator_thread (void *arg)
   return NULL;
 }
 
-static volatile int reclock_checker_done;
+static struct atomic_int reclock_checker_done;
 
 static void *
 reclock_checker_thread (void *arg)
 {
-  while (!reclock_checker_done)
+  while (get_atomic_int_value (&reclock_checker_done) == 0)
     {
       dbgprintf ("Checker %p before check lock\n", gl_thread_self_pointer ());
       gl_recursive_lock_lock (my_reclock);
@@ -497,7 +551,8 @@ test_recursive_lock (void)
   /* Initialization.  */
   for (i = 0; i < ACCOUNT_COUNT; i++)
     account[i] = 1000;
-  reclock_checker_done = 0;
+  init_atomic_int (&reclock_checker_done);
+  set_atomic_int_value (&reclock_checker_done, 0);
 
   /* Spawn the threads.  */
   checkerthread = gl_thread_create (reclock_checker_thread, NULL);
@@ -507,7 +562,7 @@ test_recursive_lock (void)
   /* Wait for the threads to terminate.  */
   for (i = 0; i < THREAD_COUNT; i++)
     gl_thread_join (threads[i], NULL);
-  reclock_checker_done = 1;
+  set_atomic_int_value (&reclock_checker_done, 1);
   gl_thread_join (checkerthread, NULL);
   check_accounts ();
 }