pthread_mutex_timedlock: New module.

* lib/pthread.in.h (pthread_mutex_timedlock): New dummy function and
new declaration.
* lib/pthread_mutex_timedlock.c: New file.
* m4/pthread_mutex_timedlock.m4: New file.
* m4/pthread.m4 (gl_PTHREAD_CHECK): Don't call AC_LIBOBJ here. Test
whether pthread_mutex_timedlock is declared.
(gl_PTHREAD_MODULE_INDICATOR): New macro.
(gl_PTHREAD_DEFAULTS): Initialize GNULIB_PTHREAD_MUTEX_TIMEDLOCK,
HAVE_PTHREAD_MUTEX_TIMEDLOCK.
* modules/pthread (configure.ac): Call AC_LIBOBJ here.
(Makefile.am): Substitute GNULIB_PTHREAD_MUTEX_TIMEDLOCK,
HAVE_PTHREAD_MUTEX_TIMEDLOCK.
* modules/pthread_mutex_timedlock: New file.
* doc/posix-functions/pthread_mutex_timedlock.texi: Mention the new
module.

1 files changed, 87 insertions, 0 deletions

diff --git a/lib/pthread_mutex_timedlock.c b/lib/pthread_mutex_timedlock.c
new file mode 100644
index 0000000000..9b6bc6355c
--- /dev/null
+++ b/lib/pthread_mutex_timedlock.c
@@ -0,0 +1,87 @@
+/* Lock a mutex, abandoning after a certain time.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <pthread.h>
+
+#include <errno.h>
+#include <limits.h>
+#include <sys/time.h>
+#include <time.h>
+
+int
+pthread_mutex_timedlock (pthread_mutex_t *mutex, const struct timespec *abstime)
+{
+  /* Poll the mutex's state in regular intervals.  Ugh.  */
+  /* POSIX says:
+      "Under no circumstance shall the function fail with a timeout if
+       the mutex can be locked immediately. The validity of the abstime
+       parameter need not be checked if the mutex can be locked
+       immediately."
+     Therefore start the loop with a pthread_mutex_trylock call.  */
+  for (;;)
+    {
+      int err;
+      struct timeval currtime;
+      unsigned long remaining;
+      struct timespec duration;
+
+      err = pthread_mutex_trylock (mutex);
+      if (err != EBUSY)
+        return err;
+
+      gettimeofday (&currtime, NULL);
+
+      if (currtime.tv_sec > abstime->tv_sec)
+        remaining = 0;
+      else
+        {
+          unsigned long seconds = abstime->tv_sec - currtime.tv_sec;
+          remaining = seconds * 1000000000;
+          if (remaining / 1000000000 != seconds) /* overflow? */
+            remaining = ULONG_MAX;
+          else
+            {
+              long nanoseconds =
+                abstime->tv_nsec - currtime.tv_usec * 1000;
+              if (nanoseconds >= 0)
+                {
+                  remaining += nanoseconds;
+                  if (remaining < nanoseconds) /* overflow? */
+                    remaining = ULONG_MAX;
+                }
+              else
+                {
+                  if (remaining >= - nanoseconds)
+                    remaining -= (- nanoseconds);
+                  else
+                    remaining = 0;
+                }
+            }
+        }
+      if (remaining == 0)
+        return ETIMEDOUT;
+
+      /* Sleep 1 ms.  */
+      duration.tv_sec = 0;
+      duration.tv_nsec = 1000000;
+      if (duration.tv_nsec > remaining)
+        duration.tv_nsec = remaining;
+      nanosleep (&duration, NULL);
+    }
+}