text: /****************************************************************************
   * arch/sim/src/up_testset.c
   *
   *   Copyright (C) 2016 Gregory Nutt. All rights reserved.
   *   Author: Gregory Nutt <gnutt@nuttx.org>
   *
   * 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 <stdint.h>
  #include <pthread.h>
  
  /****************************************************************************
   * Pre-processor Definitions
   ****************************************************************************/
  /* Must match definitions in arch/sim/include/spinlock.h */
  
  #define SP_UNLOCKED 0   /* The Un-locked state */
  #define SP_LOCKED   1   /* The Locked state */
  
  /****************************************************************************
   * Public Types
   ****************************************************************************/
  /* Must match definitions in arch/sim/include/spinlock.h */
  
  typedef uint8_t spinlock_t;
  
  /****************************************************************************
   * Private Data
   ****************************************************************************/
  
  #ifdef CONFIG_SMP
  static pthread_mutex_t g_tsmutex = PTHREAD_MUTEX_INITIALIZER;
  #endif
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: up_testset
   *
   * Description:
   *   Perform an atomic test and set operation on the provided spinlock.
   *
   *   This function must be provided via the architecture-specific logoic.
   *
   * Input Parameters:
   *   lock - The address of spinlock object.
   *
   * Returned Value:
   *   The spinlock is always locked upon return.  The value of previous value
   *   of the spinlock variable is returned, either SP_LOCKED if the spinlock
   *   as previously locked (meaning that the test-and-set operation failed to
   *   obtain the lock) or SP_UNLOCKED if the spinlock was previously unlocked
   *   (meaning that we successfully obtained the lock)
   *
   ****************************************************************************/
  
  spinlock_t up_testset(volatile spinlock_t *lock)
  {
  #ifdef CONFIG_SMP
    /* In the multi-CPU SMP case, we use a mutex to assure that the following
     * test and set is atomic.
     */
  
    (void)pthread_mutex_lock(&g_tsmutex);
  #endif
  
    /* In the non-SMP case, the simulation is implemented with a single thread
     * the test-and-set operation is inherently atomic.
     */
  
    spinlock_t ret = *lock;
    *lock = SP_LOCKED;
  
  #ifdef CONFIG_SMP
    (void)pthread_mutex_unlock(&g_tsmutex);
  #endif
    return ret;
  }
  