pthreads: Adding rwlock implementation

Adding an implementation for read/write locks into the pthread library.
These locks are writer priority, such that if any writers come in they
are given priority for writing.

libc/pthread/Make.defs

@@ -53,6 +53,10 @@ CSRCS += pthread_mutexattr_setrobust.c pthread_mutexattr_getrobust.c
 CSRCS += pthread_setcancelstate.c pthread_setcanceltype.c
 CSRCS += pthread_testcancel.c
 
+ifeq ($(CONFIG_PTHREAD_RWLOCK),y)
+CSRCS += pthread_rwlock.c pthread_rwlock_rdlock.c pthread_rwlock_wrlock.c
+endif
+
 ifeq ($(CONFIG_SMP),y)
 CSRCS += pthread_attr_getaffinity.c pthread_attr_setaffinity.c
 endif

libc/pthread/pthread_rwlock.c

@@ -0,0 +1,127 @@
+/****************************************************************************
+ * libc/pthread/pthread_rwlock.c
+ *
+ *   Copyright (C) 2017 Mark Schulte. All rights reserved.
+ *   Author: Mark Schulte <mark@mjs.pw>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdint.h>
+#include <pthread.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/semaphore.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+int pthread_rwlock_init(FAR pthread_rwlock_t *lock,
+                        FAR const pthread_rwlockattr_t *attr)
+{
+  int err;
+
+  if (attr != NULL)
+    {
+      return -ENOSYS;
+    }
+
+  lock->num_readers = 0;
+  lock->num_writers = 0;
+
+  err = pthread_cond_init(&lock->cv, NULL);
+  if (err != 0)
+    {
+      return err;
+    }
+
+  err = pthread_mutex_init(&lock->lock, NULL);
+  if (err != 0)
+    {
+      pthread_cond_destroy(&lock->cv);
+      return err;
+    }
+
+  return err;
+}
+
+int pthread_rwlock_destroy(FAR pthread_rwlock_t *lock)
+{
+  int cond_err  = pthread_cond_destroy(&lock->cv);
+  int mutex_err = pthread_mutex_destroy(&lock->lock);
+
+  if (mutex_err)
+    {
+      return mutex_err;
+    }
+
+  return cond_err;
+}
+
+int pthread_rwlock_unlock(FAR pthread_rwlock_t *rw_lock)
+{
+  int err;
+
+  err = pthread_mutex_lock(&rw_lock->lock);
+  if (err != 0)
+    {
+      return err;
+    }
+
+  if (rw_lock->num_readers > 0)
+    {
+      rw_lock->num_readers--;
+
+      if (rw_lock->num_readers == 0)
+        {
+          err = pthread_cond_broadcast(&rw_lock->cv);
+        }
+    }
+  else if (rw_lock->num_writers > 0)
+    {
+      rw_lock->num_writers--;
+
+      err = pthread_cond_broadcast(&rw_lock->cv);
+    }
+  else
+    {
+      err = EINVAL;
+    }
+
+  pthread_mutex_unlock(&rw_lock->lock);
+  return err;
+}

libc/pthread/pthread_rwlock_rdlock.c

@@ -0,0 +1,143 @@
+/****************************************************************************
+ * libc/pthread/pthread_rwlockread.c
+ *
+ *   Copyright (C) 2017 Mark Schulte. All rights reserved.
+ *   Author: Mark Schulte <mark@mjs.pw>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdint.h>
+#include <pthread.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/semaphore.h>
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+static int tryrdlock(FAR pthread_rwlock_t *rw_lock)
+{
+  int err;
+
+  if (rw_lock->num_writers > 0)
+    {
+      err = EBUSY;
+    }
+  else if (rw_lock->num_readers == UINT_MAX)
+    {
+      err = EAGAIN;
+    }
+  else
+    {
+      rw_lock->num_readers++;
+      err = OK;
+    }
+
+  return err;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: pthread_rwlock_rdlock
+ *
+ * Description:
+ *   Locks a read/write lock for reading
+ *
+ * Parameters:
+ *   None
+ *
+ * Return Value:
+ *   None
+ *
+ * Assumptions:
+ *
+ ****************************************************************************/
+
+int pthread_rwlock_tryrdlock(FAR pthread_rwlock_t *rw_lock)
+{
+  int err = pthread_mutex_trylock(&rw_lock->lock);
+
+  if (err != 0)
+    {
+      return err;
+    }
+
+  err = tryrdlock(rw_lock);
+
+  pthread_mutex_unlock(&rw_lock->lock);
+  return err;
+}
+
+int pthread_rwlock_timedrdlock(FAR pthread_rwlock_t *rw_lock,
+                               FAR const struct timespec *ts)
+{
+  int err = pthread_mutex_lock(&rw_lock->lock);
+
+  if (err != 0)
+    {
+      return err;
+    }
+
+  while ((err = tryrdlock(rw_lock)) == EBUSY)
+    {
+      if (ts != NULL)
+        {
+          err = pthread_cond_timedwait(&rw_lock->cv, &rw_lock->lock, ts);
+        }
+      else
+        {
+          err = pthread_cond_wait(&rw_lock->cv, &rw_lock->lock);
+        }
+
+      if (err != 0)
+        {
+          break;
+        }
+    }
+
+  pthread_mutex_unlock(&rw_lock->lock);
+  return err;
+}
+
+int pthread_rwlock_rdlock(FAR pthread_rwlock_t * rw_lock)
+{
+  return pthread_rwlock_timedrdlock(rw_lock, NULL);
+}

libc/pthread/pthread_rwlock_wrlock.c

@@ -0,0 +1,133 @@
+/****************************************************************************
+ * libc/pthread/pthread_rwlockwrite.c
+ *
+ *   Copyright (C) 2017 Mark Schulte. All rights reserved.
+ *   Author: Mark Schulte <mark@mjs.pw>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdint.h>
+#include <pthread.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/semaphore.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: pthread_rwlock_rdlock
+ *
+ * Description:
+ *   Locks a read/write lock for reading
+ *
+ * Parameters:
+ *   None
+ *
+ * Return Value:
+ *   None
+ *
+ * Assumptions:
+ *
+ ****************************************************************************/
+
+int pthread_rwlock_trywrlock(FAR pthread_rwlock_t *rw_lock)
+{
+  int err = pthread_mutex_trylock(&rw_lock->lock);
+
+  if (err != 0)
+    {
+      return err;
+    }
+
+  if (rw_lock->num_readers > 0 || rw_lock->num_writers > 0)
+    {
+      err = EBUSY;
+    }
+  else
+    {
+      rw_lock->num_writers++;
+    }
+
+  pthread_mutex_unlock(&rw_lock->lock);
+  return err;
+}
+
+int pthread_rwlock_timedwrlock(FAR pthread_rwlock_t *rw_lock,
+                               FAR const struct timespec *ts)
+{
+  int err = pthread_mutex_lock(&rw_lock->lock);
+  int num_writers_current;
+
+  if (err != 0)
+    {
+      return err;
+    }
+
+  num_writers_current = rw_lock->num_writers++;
+  if (num_writers_current == 0)
+    {
+      goto exit_with_mutex;
+    }
+
+  while (rw_lock->num_writers != num_writers_current)
+    {
+      if (ts != NULL)
+        {
+          err = pthread_cond_timedwait(&rw_lock->cv, &rw_lock->lock, ts);
+        }
+      else
+        {
+          err = pthread_cond_wait(&rw_lock->cv, &rw_lock->lock);
+        }
+
+      if (err != 0)
+        {
+          break;
+        }
+    }
+
+exit_with_mutex:
+  pthread_mutex_unlock(&rw_lock->lock);
+  return err;
+}
+
+int pthread_rwlock_wrlock(FAR pthread_rwlock_t *rw_lock)
+{
+  return pthread_rwlock_timedwrlock(rw_lock, NULL);
+}