565 lines
15 KiB
C
565 lines
15 KiB
C
/****************************************************************************
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* sched/semaphore/spinlock.c
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*
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* Copyright (C) 2016 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <sched.h>
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#include <assert.h>
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#include <nuttx/spinlock.h>
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#include <nuttx/sched_note.h>
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#include <arch/irq.h>
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#include "sched/sched.h"
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#ifdef CONFIG_SPINLOCK
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define IMPOSSIBLE_CPU 0xff
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/* REVISIT: What happens if a thread taks a spinlock while running on one
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* CPU, but is suspended, then reassigned to another CPU where it runs and
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* eventually calls spin_unlock(). One solution might be to lock a thread to
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* a CPU if it holds a spinlock. That would assure that it never runs on
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* any other CPU and avoids such complexities.
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*/
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#undef CONFIG_SPINLOCK_LOCKDOWN /* Feature not yet available */
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: spin_initializer
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*
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* Description:
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* Initialize a re-entrant spinlock object to its initial, unlocked state.
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*
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* Input Parameters:
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* lock - A reference to the spinlock object to be initialized.
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*
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* Returned Value:
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* None.
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*
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****************************************************************************/
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void spin_initializer(FAR struct spinlock_s *lock)
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{
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DEBUGASSERT(lock != NULL);
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lock->sp_lock = SP_UNLOCKED;
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#ifdef CONFIG_SMP
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lock->sp_cpu = IMPOSSIBLE_CPU;
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lock->sp_count = 0;
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#endif
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}
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/****************************************************************************
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* Name: spin_lock
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*
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* Description:
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* If this CPU does not already hold the spinlock, then loop until the
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* spinlock is successfully locked.
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*
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* This implementation is non-reentrant and is prone to deadlocks in
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* the case that any logic on the same CPU attempts to take the lock
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* more than one
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*
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* Input Parameters:
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* lock - A reference to the spinlock object to lock.
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*
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* Returned Value:
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* None. When the function returns, the spinlock was successfully locked
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* by this CPU.
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*
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* Assumptions:
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* Not running at the interrupt level.
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*
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****************************************************************************/
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void spin_lock(FAR volatile spinlock_t *lock)
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{
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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/* Notify that we are waiting for a spinlock */
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sched_note_spinlock(this_task(), lock);
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#endif
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while (up_testset(lock) == SP_LOCKED)
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{
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SP_DSB();
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}
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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/* Notify that we have the spinlock */
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sched_note_spinlocked(this_task(), lock);
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#endif
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SP_DMB();
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}
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/****************************************************************************
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* Name: spin_lock_wo_note
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*
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* Description:
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* If this CPU does not already hold the spinlock, then loop until the
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* spinlock is successfully locked.
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*
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* This implementation is the same as the above spin_lock() except that
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* it does not perform instrumentation logic.
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*
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* Input Parameters:
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* lock - A reference to the spinlock object to lock.
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*
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* Returned Value:
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* None. When the function returns, the spinlock was successfully locked
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* by this CPU.
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*
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* Assumptions:
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* Not running at the interrupt level.
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*
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****************************************************************************/
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void spin_lock_wo_note(FAR volatile spinlock_t *lock)
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{
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while (up_testset(lock) == SP_LOCKED)
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{
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SP_DSB();
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}
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SP_DMB();
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}
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/****************************************************************************
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* Name: spin_unlock
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*
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* Description:
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* Release one count on a non-reentrant spinlock.
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*
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* Input Parameters:
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* lock - A reference to the spinlock object to unlock.
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*
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* Returned Value:
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* None.
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*
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* Assumptions:
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* Not running at the interrupt level.
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*
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****************************************************************************/
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#ifdef __SP_UNLOCK_FUNCTION
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void spin_unlock(FAR volatile spinlock_t *lock)
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{
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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/* Notify that we are unlocking the spinlock */
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sched_note_spinunlock(this_task(), lock);
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#endif
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SP_DMB();
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*lock = SP_UNLOCKED;
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SP_DSB();
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}
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#endif
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/****************************************************************************
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* Name: spin_unlock_wo_note
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*
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* Description:
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* Release one count on a non-reentrant spinlock.
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*
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* This implementation is the same as the above spin_unlock() except that
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* it does not perform instrumentation logic.
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*
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* Input Parameters:
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* lock - A reference to the spinlock object to unlock.
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*
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* Returned Value:
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* None.
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*
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* Assumptions:
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* Not running at the interrupt level.
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*
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****************************************************************************/
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void spin_unlock_wo_note(FAR volatile spinlock_t *lock)
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{
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SP_DMB();
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*lock = SP_UNLOCKED;
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SP_DSB();
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}
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/****************************************************************************
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* Name: spin_lockr
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*
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* Description:
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* If this CPU does not already hold the spinlock, then loop until the
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* spinlock is successfully locked.
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*
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* This implementation is re-entrant in the sense that it can called
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* numerous times from the same CPU without blocking. Of course,
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* spin_unlock() must be called the same number of times. NOTE: the
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* thread that originallly took the look may be executing on a different
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* CPU when it unlocks the spinlock.
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*
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* Input Parameters:
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* lock - A reference to the spinlock object to lock.
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*
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* Returned Value:
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* None. When the function returns, the spinlock was successfully locked
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* by this CPU.
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*
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* Assumptions:
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* Not running at the interrupt level.
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*
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****************************************************************************/
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void spin_lockr(FAR struct spinlock_s *lock)
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{
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#ifdef CONFIG_SMP
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irqstate_t flags;
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uint8_t cpu = this_cpu();
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/* Disable interrupts (all CPUs) */
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flags = up_irq_save();
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/* Do we already hold the lock on this CPU? */
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if (lock->sp_cpu == cpu)
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{
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/* Yes... just increment the number of references we have on the lock */
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lock->sp_count++;
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DEBUGASSERT(lock->sp_lock = SP_LOCKED && lock->sp_count > 0);
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}
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else
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{
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#ifdef CONFIG_SPINLOCK_LOCKDOWN
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/* REVISIT: What happens if this thread is suspended, then reassigned
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* to another CPU where it runs and eventually calls spin_unlock().
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* One solution might be to lock a thread to a CPU if it holds a
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* spinlock. That would assure that it never runs on any other CPU
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* and avoids such complexities.
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*/
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# warning Missing logic
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#endif
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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/* Notify that we are waiting for a spinlock */
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sched_note_spinlock(this_task(), &lock->sp_lock);
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#endif
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/* Take the lock. REVISIT: We should set an indication in the TCB
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* that the thread is spinning. This might be useful in determining
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* some scheduling actions?
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*/
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while (up_testset(&lock->sp_lock) == SP_LOCKED)
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{
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up_irq_restore(flags);
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sched_yield();
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flags = up_irq_save();
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SP_DSB();
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}
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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/* Notify that we have thespinlock */
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sched_note_spinlocked(this_task(), &lock->sp_lock);
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#endif
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SP_DMB();
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/* Take one count on the lock */
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lock->sp_cpu = cpu;
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lock->sp_count = 1;
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}
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up_irq_restore(flags);
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#else /* CONFIG_SMP */
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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/* Notify that we are waiting for a spinlock */
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sched_note_spinlock(this_task(), &lock->sp_lock);
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#endif
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/* Take the lock. REVISIT: We should set an indication in the TCB that
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* the thread is spinning. This might be useful in determining some
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* scheduling actions?
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*/
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while (up_testset(&lock->sp_lock) == SP_LOCKED)
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{
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sched_yield();
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SP_DSB()
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}
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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/* Notify that we have thespinlock */
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sched_note_spinlocked(this_task(), &lock->sp_lock);
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#endif
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SP_DMB();
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#endif /* CONFIG_SMP */
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}
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/****************************************************************************
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* Name: spin_unlockr
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*
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* Description:
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* Release one count on a spinlock.
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*
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* Input Parameters:
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* lock - A reference to the spinlock object to unlock.
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*
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* Returned Value:
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* None.
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*
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* Assumptions:
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* Not running at the interrupt level.
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*
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****************************************************************************/
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void spin_unlockr(FAR struct spinlock_s *lock)
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{
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#ifdef CONFIG_SMP
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irqstate_t flags;
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#ifdef CONFIG_SPINLOCK_LOCKDOWN
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uint8_t cpu = this_cpu();
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#endif
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/* Disable interrupts (all CPUs) */
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flags = up_irq_save();
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#ifdef CONFIG_SPINLOCK_LOCKDOWN
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/* REVISIT: What happens if this thread took the lock on a different CPU,
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* was suspended, then reassigned to this CPU where it runs and eventually
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* calls spin_unlock(). One solution might be to lock a thread to a CPU if
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* it holds a spinlock. That would assure that it never runs on any other
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* CPU and avoids such complexities.
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*/
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DEBUGASSERT(lock != NULL && lock->sp_lock == SP_LOCKED &&
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lock->sp_cpu == this_cpu() && lock->sp_count > 0);
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/* Do we already hold the lock? */
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if (lock->sp_cpu == cpu)
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#else
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/* The alternative is to allow the lock to be released from any CPU */
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DEBUGASSERT(lock != NULL && lock->sp_lock == SP_LOCKED &&
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lock->sp_count > 0);
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#endif
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{
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/* Yes... just decrement the number of references we have on the lock */
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if (lock->sp_count <= 1)
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{
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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/* Notify that we are unlocking the spinlock */
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sched_note_spinunlock(this_task(), &lock->sp_lock);
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#endif
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/* The count must decremented to zero */
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lock->sp_count = 0;
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lock->sp_cpu = IMPOSSIBLE_CPU;
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lock->sp_lock = SP_UNLOCKED;
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}
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else
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{
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lock->sp_count--;
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}
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}
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up_irq_restore(flags);
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#else /* CONFIG_SMP */
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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/* Notify that we are unlocking the spinlock */
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sched_note_spinunlock(this_task(), &lock->sp_lock);
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#endif
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/* Just mark the spinlock unlocked */
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DEBUGASSERT(lock != NULL && lock->sp_lock == SP_LOCKED);
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lock->sp_lock = SP_UNLOCKED;
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#endif /* CONFIG_SMP */
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}
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/****************************************************************************
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* Name: spin_setbit
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*
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* Description:
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* Makes setting a CPU bit in a bitset an atomic action
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*
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* Input Parameters:
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* set - A reference to the bitset to set the CPU bit in
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* cpu - The bit number to be set
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* setlock - A reference to the lock protecting the set
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* orlock - Will be set to SP_LOCKED while holding setlock
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void spin_setbit(FAR volatile cpu_set_t *set, unsigned int cpu,
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FAR volatile spinlock_t *setlock,
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FAR volatile spinlock_t *orlock)
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{
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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cpu_set_t prev;
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#endif
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irqstate_t flags;
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/* Disable local interrupts to prevent being re-entered from an interrupt
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* on the same CPU. This may not effect interrupt behavior on other CPUs.
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*/
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flags = up_irq_save();
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/* Then, get the 'setlock' spinlock */
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spin_lock(setlock);
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/* Then set the bit and mark the 'orlock' as locked */
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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prev = *set;
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#endif
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*set |= (1 << cpu);
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*orlock = SP_LOCKED;
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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if (prev == 0)
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{
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/* Notify that we have locked the spinlock */
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sched_note_spinlocked(this_task(), orlock);
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}
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#endif
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/* Release the 'setlock' and restore local interrupts */
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spin_unlock(setlock);
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up_irq_restore(flags);
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}
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/****************************************************************************
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* Name: spin_clrbit
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*
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* Description:
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* Makes clearing a CPU bit in a bitset an atomic action
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*
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* Input Parameters:
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* set - A reference to the bitset to set the CPU bit in
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* cpu - The bit number to be set
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* setlock - A reference to the lock protecting the set
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* orlock - Will be set to SP_UNLOCKED if all bits become cleared in set
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void spin_clrbit(FAR volatile cpu_set_t *set, unsigned int cpu,
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FAR volatile spinlock_t *setlock,
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FAR volatile spinlock_t *orlock)
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{
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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cpu_set_t prev;
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#endif
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irqstate_t flags;
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/* Disable local interrupts to prevent being re-entered from an interrupt
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* on the same CPU. This may not effect interrupt behavior on other CPUs.
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*/
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flags = up_irq_save();
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/* First, get the 'setlock' spinlock */
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spin_lock(setlock);
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/* Then clear the bit in the CPU set. Set/clear the 'orlock' depending
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* upon the resulting state of the CPU set.
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*/
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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prev = *set;
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#endif
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*set &= ~(1 << cpu);
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*orlock = (*set != 0) ? SP_LOCKED : SP_UNLOCKED;
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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if (prev != 0 && *set == 0)
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{
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/* Notify that we have unlocked the spinlock */
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sched_note_spinunlock(this_task(), orlock);
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}
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#endif
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/* Release the 'setlock' and restore local interrupts */
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spin_unlock(setlock);
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up_irq_restore(flags);
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}
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#endif /* CONFIG_SPINLOCK */
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