1 files changed, 55 insertions, 0 deletions
diff --git a/sysdeps/htl/pt-rwlock-tryrdlock.c b/sysdeps/htl/pt-rwlock-tryrdlock.c
new file mode 100644
index 0000000000..39a368c7c1
--- /dev/null
+++ b/sysdeps/htl/pt-rwlock-tryrdlock.c
@@ -0,0 +1,55 @@
+/* Try to acquire a rwlock for reading.  Generic version.
+   Copyright (C) 2002-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#include <pthread.h>
+#include <assert.h>
+
+#include <pt-internal.h>
+
+/* Try to acquire RWLOCK.  */
+int
+pthread_rwlock_tryrdlock (struct __pthread_rwlock *rwlock)
+{
+  __pthread_spin_lock (&rwlock->__lock);
+  if (__pthread_spin_trylock (&rwlock->__held) == 0)
+    /* Successfully acquired the lock.  */
+    {
+      assert (rwlock->__readerqueue == 0);
+      assert (rwlock->__writerqueue == 0);
+      assert (rwlock->__readers == 0);
+
+      rwlock->__readers = 1;
+      __pthread_spin_unlock (&rwlock->__lock);
+      return 0;
+    }
+  else
+    /* Lock is held, but is held by a reader?  */
+  if (rwlock->__readers > 0)
+    {
+      assert (rwlock->__readerqueue == 0);
+      rwlock->__readers++;
+      __pthread_spin_unlock (&rwlock->__lock);
+      return 0;
+    }
+
+  /* The lock is busy.  */
+
+  __pthread_spin_unlock (&rwlock->__lock);
+
+  return EBUSY;
+}