nuttx/sched/semaphore/spinlock.c

/****************************************************************************
 * sched/semaphore/spinlock.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <sys/types.h>
#include <sched.h>
#include <assert.h>

#include <nuttx/spinlock.h>
#include <nuttx/sched_note.h>
#include <arch/irq.h>

#include "sched/sched.h"

#ifdef CONFIG_SPINLOCK

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: spin_lock
 *
 * Description:
 *   If this CPU does not already hold the spinlock, then loop until the
 *   spinlock is successfully locked.
 *
 *   This implementation is non-reentrant and is prone to deadlocks in
 *   the case that any logic on the same CPU attempts to take the lock
 *   more than once.
 *
 * Input Parameters:
 *   lock - A reference to the spinlock object to lock.
 *
 * Returned Value:
 *   None.  When the function returns, the spinlock was successfully locked
 *   by this CPU.
 *
 * Assumptions:
 *   Not running at the interrupt level.
 *
 ****************************************************************************/

void spin_lock(FAR volatile spinlock_t *lock)
{
#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
  /* Notify that we are waiting for a spinlock */

  sched_note_spinlock(this_task(), lock);
#endif

  while (up_testset(lock) == SP_LOCKED)
    {
      SP_DSB();
      SP_WFE();
    }

#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
  /* Notify that we have the spinlock */

  sched_note_spinlocked(this_task(), lock);
#endif
  SP_DMB();
}

/****************************************************************************
 * Name: spin_lock_wo_note
 *
 * Description:
 *   If this CPU does not already hold the spinlock, then loop until the
 *   spinlock is successfully locked.
 *
 *   This implementation is the same as the above spin_lock() except that
 *   it does not perform instrumentation logic.
 *
 * Input Parameters:
 *   lock - A reference to the spinlock object to lock.
 *
 * Returned Value:
 *   None.  When the function returns, the spinlock was successfully locked
 *   by this CPU.
 *
 * Assumptions:
 *   Not running at the interrupt level.
 *
 ****************************************************************************/

void spin_lock_wo_note(FAR volatile spinlock_t *lock)
{
  while (up_testset(lock) == SP_LOCKED)
    {
      SP_DSB();
      SP_WFE();
    }

  SP_DMB();
}

/****************************************************************************
 * Name: spin_trylock
 *
 * Description:
 *   Try once to lock the spinlock.  Do not wait if the spinlock is already
 *   locked.
 *
 * Input Parameters:
 *   lock - A reference to the spinlock object to lock.
 *
 * Returned Value:
 *   SP_LOCKED   - Failure, the spinlock was already locked
 *   SP_UNLOCKED - Success, the spinlock was successfully locked
 *
 * Assumptions:
 *   Not running at the interrupt level.
 *
 ****************************************************************************/

spinlock_t spin_trylock(FAR volatile spinlock_t *lock)
{
#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
  /* Notify that we are waiting for a spinlock */

  sched_note_spinlock(this_task(), lock);
#endif

  if (up_testset(lock) == SP_LOCKED)
    {
#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
      /* Notify that we abort for a spinlock */

      sched_note_spinabort(this_task(), &lock);
#endif
      SP_DSB();
      return SP_LOCKED;
    }

#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
  /* Notify that we have the spinlock */

  sched_note_spinlocked(this_task(), lock);
#endif
  SP_DMB();
  return SP_UNLOCKED;
}

/****************************************************************************
 * Name: spin_trylock_wo_note
 *
 * Description:
 *   Try once to lock the spinlock.  Do not wait if the spinlock is already
 *   locked.
 *
 *   This implementation is the same as the above spin_trylock() except that
 *   it does not perform instrumentation logic.
 *
 * Input Parameters:
 *   lock - A reference to the spinlock object to lock.
 *
 * Returned Value:
 *   SP_LOCKED   - Failure, the spinlock was already locked
 *   SP_UNLOCKED - Success, the spinlock was successfully locked
 *
 * Assumptions:
 *   Not running at the interrupt level.
 *
 ****************************************************************************/

spinlock_t spin_trylock_wo_note(FAR volatile spinlock_t *lock)
{
  if (up_testset(lock) == SP_LOCKED)
    {
      SP_DSB();
      return SP_LOCKED;
    }

  SP_DMB();
  return SP_UNLOCKED;
}

/****************************************************************************
 * Name: spin_unlock
 *
 * Description:
 *   Release one count on a non-reentrant spinlock.
 *
 * Input Parameters:
 *   lock - A reference to the spinlock object to unlock.
 *
 * Returned Value:
 *   None.
 *
 * Assumptions:
 *   Not running at the interrupt level.
 *
 ****************************************************************************/

#ifdef __SP_UNLOCK_FUNCTION
void spin_unlock(FAR volatile spinlock_t *lock)
{
#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
  /* Notify that we are unlocking the spinlock */

  sched_note_spinunlock(this_task(), lock);
#endif

  SP_DMB();
  *lock = SP_UNLOCKED;
  SP_DSB();
  SP_SEV();
}
#endif

/****************************************************************************
 * Name: spin_unlock_wo_note
 *
 * Description:
 *   Release one count on a non-reentrant spinlock.
 *
 *   This implementation is the same as the above spin_unlock() except that
 *   it does not perform instrumentation logic.
 *
 * Input Parameters:
 *   lock - A reference to the spinlock object to unlock.
 *
 * Returned Value:
 *   None.
 *
 * Assumptions:
 *   Not running at the interrupt level.
 *
 ****************************************************************************/

void spin_unlock_wo_note(FAR volatile spinlock_t *lock)
{
  SP_DMB();
  *lock = SP_UNLOCKED;
  SP_DSB();
  SP_SEV();
}

/****************************************************************************
 * Name: spin_setbit
 *
 * Description:
 *   Makes setting a CPU bit in a bitset an atomic action
 *
 * Input Parameters:
 *   set     - A reference to the bitset to set the CPU bit in
 *   cpu     - The bit number to be set
 *   setlock - A reference to the lock protecting the set
 *   orlock  - Will be set to SP_LOCKED while holding setlock
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

#ifdef CONFIG_SMP
void spin_setbit(FAR volatile cpu_set_t *set, unsigned int cpu,
                 FAR volatile spinlock_t *setlock,
                 FAR volatile spinlock_t *orlock)
{
#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
  cpu_set_t prev;
#endif
  irqstate_t flags;

  /* Disable local interrupts to prevent being re-entered from an interrupt
   * on the same CPU.  This may not effect interrupt behavior on other CPUs.
   */

  flags = up_irq_save();

  /* Then, get the 'setlock' spinlock */

  spin_lock(setlock);

  /* Then set the bit and mark the 'orlock' as locked */

#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
  prev    = *set;
#endif
  *set   |= (1 << cpu);
  *orlock = SP_LOCKED;

#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
  if (prev == 0)
    {
      /* Notify that we have locked the spinlock */

      sched_note_spinlocked(this_task(), orlock);
    }
#endif

  /* Release the 'setlock' and restore local interrupts */

  spin_unlock(setlock);
  up_irq_restore(flags);
}
#endif

/****************************************************************************
 * Name: spin_clrbit
 *
 * Description:
 *   Makes clearing a CPU bit in a bitset an atomic action
 *
 * Input Parameters:
 *   set     - A reference to the bitset to set the CPU bit in
 *   cpu     - The bit number to be set
 *   setlock - A reference to the lock protecting the set
 *   orlock  - Will be set to SP_UNLOCKED if all bits become cleared in set
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

#ifdef CONFIG_SMP
void spin_clrbit(FAR volatile cpu_set_t *set, unsigned int cpu,
                 FAR volatile spinlock_t *setlock,
                 FAR volatile spinlock_t *orlock)
{
#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
  cpu_set_t prev;
#endif
  irqstate_t flags;

  /* Disable local interrupts to prevent being re-entered from an interrupt
   * on the same CPU.  This may not effect interrupt behavior on other CPUs.
   */

  flags = up_irq_save();

  /* First, get the 'setlock' spinlock */

  spin_lock(setlock);

  /* Then clear the bit in the CPU set.  Set/clear the 'orlock' depending
   * upon the resulting state of the CPU set.
   */

#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
  prev    = *set;
#endif
  *set   &= ~(1 << cpu);
  *orlock = (*set != 0) ? SP_LOCKED : SP_UNLOCKED;

#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
  if (prev != 0 && *set == 0)
    {
      /* Notify that we have unlocked the spinlock */

      sched_note_spinunlock(this_task(), orlock);
    }
#endif

  /* Release the 'setlock' and restore local interrupts */

  spin_unlock(setlock);
  up_irq_restore(flags);
}
#endif

#endif /* CONFIG_SPINLOCK */