1 files changed, 95 insertions, 0 deletions
diff --git a/nptl/pthread_rwlock_rdlock.c b/nptl/pthread_rwlock_rdlock.c
new file mode 100644
index 0000000000..e225d7030d
--- /dev/null
+++ b/nptl/pthread_rwlock_rdlock.c
@@ -0,0 +1,95 @@
+/* Copyright (C) 2003, 2004 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <errno.h>
+#include <sysdep.h>
+#include <lowlevellock.h>
+#include <pthread.h>
+#include <pthreadP.h>
+
+
+/* Acquire read lock for RWLOCK.  */
+int
+__pthread_rwlock_rdlock (rwlock)
+     pthread_rwlock_t *rwlock;
+{
+  int result = 0;
+
+  /* Make sure we are along.  */
+  lll_mutex_lock (rwlock->__data.__lock);
+
+  while (1)
+    {
+      /* Get the rwlock if there is no writer...  */
+      if (rwlock->__data.__writer == 0
+	  /* ...and if either no writer is waiting or we prefer readers.  */
+	  && (!rwlock->__data.__nr_writers_queued
+	      || rwlock->__data.__flags == 0))
+	{
+	  /* Increment the reader counter.  Avoid overflow.  */
+	  if (__builtin_expect (++rwlock->__data.__nr_readers == 0, 0))
+	    {
+	      /* Overflow on number of readers.	 */
+	      --rwlock->__data.__nr_readers;
+	      result = EAGAIN;
+	    }
+
+	  break;
+	}
+
+      /* Make sure we are not holding the rwlock as a writer.  This is
+	 a deadlock situation we recognize and report.  */
+      if (__builtin_expect (rwlock->__data.__writer
+			    == THREAD_GETMEM (THREAD_SELF, tid), 0))
+	{
+	  result = EDEADLK;
+	  break;
+	}
+
+      /* Remember that we are a reader.  */
+      if (__builtin_expect (++rwlock->__data.__nr_readers_queued == 0, 0))
+	{
+	  /* Overflow on number of queued readers.  */
+	  --rwlock->__data.__nr_readers_queued;
+	  result = EAGAIN;
+	  break;
+	}
+
+      int waitval = rwlock->__data.__readers_wakeup;
+
+      /* Free the lock.  */
+      lll_mutex_unlock (rwlock->__data.__lock);
+
+      /* Wait for the writer to finish.  */
+      lll_futex_wait (&rwlock->__data.__readers_wakeup, waitval);
+
+      /* Get the lock.  */
+      lll_mutex_lock (rwlock->__data.__lock);
+
+      --rwlock->__data.__nr_readers_queued;
+    }
+
+  /* We are done, free the lock.  */
+  lll_mutex_unlock (rwlock->__data.__lock);
+
+  return result;
+}
+
+weak_alias (__pthread_rwlock_rdlock, pthread_rwlock_rdlock)
+strong_alias (__pthread_rwlock_rdlock, __pthread_rwlock_rdlock_internal)