372 lines
11 KiB
C
372 lines
11 KiB
C
/****************************************************************************
|
|
* sched/semaphore/spinlock.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 <nuttx/config.h>
|
|
|
|
#include <sys/types.h>
|
|
#include <sched.h>
|
|
#include <assert.h>
|
|
|
|
#include <nuttx/spinlock.h>
|
|
#include <arch/irq.h>
|
|
|
|
#include "sched/sched.h"
|
|
|
|
#ifdef CONFIG_SPINLOCK
|
|
|
|
/****************************************************************************
|
|
* Pre-processor Definitions
|
|
****************************************************************************/
|
|
|
|
#define IMPOSSIBLE_CPU 0xff
|
|
|
|
/* REVISIT: What happens if a thread taks a spinlock while running on one
|
|
* CPU, but is suspended, then reassigned to another CPU where it runs and
|
|
* eventually calls spin_unlock(). One solution might be to lock a thread to
|
|
* a CPU if it holds a spinlock. That would assure that it never runs on
|
|
* any other CPU and avoids such complexities.
|
|
*/
|
|
|
|
#undef CONFIG_SPINLOCK_LOCKDOWN /* Feature not yet available */
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: spin_initializer
|
|
*
|
|
* Description:
|
|
* Initialize a re-entrant spinlock object to its initial, unlocked state.
|
|
*
|
|
* Input Parameters:
|
|
* lock - A reference to the spinlock object to be initialized.
|
|
*
|
|
* Returned Value:
|
|
* None.
|
|
*
|
|
****************************************************************************/
|
|
|
|
void spin_initializer(FAR struct spinlock_s *lock)
|
|
{
|
|
DEBUGASSERT(lock != NULL);
|
|
|
|
lock->sp_lock = SP_UNLOCKED;
|
|
#ifdef CONFIG_SMP
|
|
lock->sp_cpu = IMPOSSIBLE_CPU;
|
|
lock->sp_count = 0;
|
|
#endif
|
|
}
|
|
|
|
/****************************************************************************
|
|
* 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 one
|
|
*
|
|
* 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)
|
|
{
|
|
while (up_testset(lock) == SP_LOCKED)
|
|
{
|
|
#if 0 /* Would recurse */
|
|
sched_yield();
|
|
#endif
|
|
}
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: spin_lockr
|
|
*
|
|
* Description:
|
|
* If this CPU does not already hold the spinlock, then loop until the
|
|
* spinlock is successfully locked.
|
|
*
|
|
* This implementation is re-entrant in the sense that it can called
|
|
* numerous times from the same CPU without blocking. Of course,
|
|
* spin_unlock() must be called the same number of times. NOTE: the
|
|
* thread that originallly took the look may be executing on a different
|
|
* CPU when it unlocks the spinlock.
|
|
*
|
|
* 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_lockr(FAR struct spinlock_s *lock)
|
|
{
|
|
#ifdef CONFIG_SMP
|
|
irqstate_t flags;
|
|
uint8_t cpu = this_cpu();
|
|
|
|
/* Disable interrupts (all CPUs) */
|
|
|
|
flags = up_irq_save();
|
|
|
|
/* Do we already hold the lock on this CPU? */
|
|
|
|
if (lock->sp_cpu == cpu)
|
|
{
|
|
/* Yes... just increment the number of references we have on the lock */
|
|
|
|
lock->sp_count++;
|
|
DEBUGASSERT(lock->sp_lock = SP_LOCKED && lock->sp_count > 0);
|
|
}
|
|
else
|
|
{
|
|
#ifdef CONFIG_SPINLOCK_LOCKDOWN
|
|
/* REVISIT: What happens if this thread is suspended, then reassigned
|
|
* to another CPU where it runs and eventually calls spin_unlock().
|
|
* One solution might be to lock a thread to a CPU if it holds a
|
|
* spinlock. That would assure that it never runs on any other CPU
|
|
* and avoids such complexities.
|
|
*/
|
|
|
|
# warning Missing logic
|
|
#endif
|
|
/* Take the lock. REVISIT: We should set an indication in the TCB
|
|
* that the thread is spinning. This might be useful in determining
|
|
* some scheduling actions?
|
|
*/
|
|
|
|
while (up_testset(&lock->sp_lock) == SP_LOCKED)
|
|
{
|
|
up_irq_restore(flags);
|
|
sched_yield();
|
|
flags = up_irq_save();
|
|
}
|
|
|
|
/* Take one count on the lock */
|
|
|
|
lock->sp_cpu = cpu;
|
|
lock->sp_count = 1;
|
|
}
|
|
|
|
up_irq_restore(flags);
|
|
|
|
#else /* CONFIG_SMP */
|
|
|
|
/* Take the lock. REVISIT: We should set an indication in the TCB that
|
|
* the thread is spinning. This might be useful in determining some
|
|
* scheduling actions?
|
|
*/
|
|
|
|
while (up_testset(&lock->sp_lock) == SP_LOCKED)
|
|
{
|
|
sched_yield();
|
|
}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: spin_unlockr
|
|
*
|
|
* Description:
|
|
* Release one count on a spinlock.
|
|
*
|
|
* Input Parameters:
|
|
* lock - A reference to the spinlock object to unlock.
|
|
*
|
|
* Returned Value:
|
|
* None.
|
|
*
|
|
* Assumptions:
|
|
* Not running at the interrupt level.
|
|
*
|
|
****************************************************************************/
|
|
|
|
void spin_unlockr(FAR struct spinlock_s *lock)
|
|
{
|
|
#ifdef CONFIG_SMP
|
|
irqstate_t flags;
|
|
#ifdef CONFIG_SPINLOCK_LOCKDOWN
|
|
uint8_t cpu = this_cpu();
|
|
#endif
|
|
|
|
/* Disable interrupts (all CPUs) */
|
|
|
|
flags = up_irq_save();
|
|
|
|
#ifdef CONFIG_SPINLOCK_LOCKDOWN
|
|
/* REVISIT: What happens if this thread took the lock on a different CPU,
|
|
* was suspended, then reassigned to this CPU where it runs and eventually
|
|
* calls spin_unlock(). One solution might be to lock a thread to a CPU if
|
|
* it holds a spinlock. That would assure that it never runs on any other
|
|
* CPU and avoids such complexities.
|
|
*/
|
|
|
|
DEBUGASSERT(lock != NULL && lock->sp_lock == SP_LOCKED &&
|
|
lock->sp_cpu == this_cpu() && lock->sp_count > 0);
|
|
|
|
/* Do we already hold the lock? */
|
|
|
|
if (lock->sp_cpu == cpu)
|
|
#else
|
|
/* The alternative is to allow the lock to be released from any CPU */
|
|
|
|
DEBUGASSERT(lock != NULL && lock->sp_lock == SP_LOCKED &&
|
|
lock->sp_count > 0);
|
|
#endif
|
|
|
|
{
|
|
/* Yes... just decrement the number of references we have on the lock */
|
|
|
|
if (lock->sp_count <= 1)
|
|
{
|
|
/* The count must decremented to zero */
|
|
|
|
lock->sp_count = 0;
|
|
lock->sp_cpu = IMPOSSIBLE_CPU;
|
|
lock->sp_lock = SP_UNLOCKED;
|
|
}
|
|
else
|
|
{
|
|
lock->sp_count--;
|
|
}
|
|
}
|
|
|
|
up_irq_restore(flags);
|
|
|
|
#else /* CONFIG_SMP */
|
|
/* Just mark the spinlock unlocked */
|
|
|
|
DEBUGASSERT(lock != NULL && lock->sp_lock == SP_LOCKED);
|
|
lock->sp_lock = SP_UNLOCKED;
|
|
|
|
#endif /* CONFIG_SMP */
|
|
}
|
|
|
|
/****************************************************************************
|
|
* 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 lock protecting the set
|
|
* orlock - Will be set to SP_LOCKED while holding setlock
|
|
*
|
|
* Returned Value:
|
|
* None
|
|
*
|
|
****************************************************************************/
|
|
|
|
void spin_setbit(FAR volatile cpu_set_t *set, unsigned int cpu,
|
|
FAR volatile spinlock_t *setlock,
|
|
FAR volatile spinlock_t *orlock)
|
|
{
|
|
/* First, get the 'setlock' spinlock */
|
|
|
|
spin_lock(setlock);
|
|
|
|
/* Then set the bit and mark the 'orlock' as locked */
|
|
|
|
*set |= (1 << cpu);
|
|
*orlock = SP_LOCKED;
|
|
|
|
/* Release the 'setlock' */
|
|
|
|
spin_unlock(setlock);
|
|
}
|
|
|
|
/****************************************************************************
|
|
* 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 lock protecting the set
|
|
* orlock - Will be set to SP_UNLOCKED if all bits become cleared in set
|
|
*
|
|
* Returned Value:
|
|
* None
|
|
*
|
|
****************************************************************************/
|
|
|
|
void spin_clrbit(FAR volatile cpu_set_t *set, unsigned int cpu,
|
|
FAR volatile spinlock_t *setlock,
|
|
FAR volatile spinlock_t *orlock)
|
|
{
|
|
/* 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.
|
|
*/
|
|
|
|
*set &= ~(1 << cpu);
|
|
*orlock = (*set != 0) ? SP_LOCKED : SP_UNLOCKED;
|
|
|
|
/* Release the 'setlock' */
|
|
|
|
spin_unlock(setlock);
|
|
}
|
|
|
|
#endif /* CONFIG_SPINLOCK */
|