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/*
* Copyright (c) 2012-2018 Richard Braun.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*
* Spin locks.
*
* Critical sections built with spin locks run with preemption disabled.
* Critical sections built with different spin locks may safely nest.
*
* This module provides fair spin locks which guarantee time-bounded lock
* acquisition depending only on the number of contending processors.
*/
#ifndef KERN_SPINLOCK_H
#define KERN_SPINLOCK_H
#include <assert.h>
#include <stdbool.h>
#include <stdint.h>
#include <kern/atomic.h>
#include <kern/init.h>
#include <kern/macros.h>
#include <kern/spinlock_i.h>
#include <kern/spinlock_types.h>
#include <kern/thread.h>
struct spinlock;
static inline bool
spinlock_locked(const struct spinlock *lock)
{
uint32_t value;
value = atomic_load(&lock->value, ATOMIC_RELAXED);
return value != SPINLOCK_UNLOCKED;
}
#ifdef SPINLOCK_TRACK_OWNER
static inline void
spinlock_transfer_owner(struct spinlock *lock, struct thread *owner)
{
assert(lock->owner == thread_self());
lock->owner = owner;
}
#else /* SPINLOCK_TRACK_OWNER */
#define spinlock_transfer_owner(lock, owner)
#endif /* SPINLOCK_TRACK_OWNER */
/*
* Initialize a spin lock.
*/
void spinlock_init(struct spinlock *lock);
/*
* Attempt to lock the given spin lock.
*
* Return 0 on success, EBUSY if the spin lock is already locked.
*
* If the operation succeeds, prior unlock operations on the same spin lock
* synchronize with this operation.
*/
static inline int
spinlock_trylock(struct spinlock *lock)
{
int error;
thread_preempt_disable();
error = spinlock_lock_fast(lock);
if (unlikely(error)) {
thread_preempt_enable();
}
return error;
}
/*
* Lock a spin lock.
*
* If the spin lock is already locked, the calling thread spins until the
* spin lock is unlocked.
*
* A spin lock can only be locked once.
*
* Prior unlock operations on the same spin lock synchronize with this
* operation.
*/
static inline void
spinlock_lock(struct spinlock *lock)
{
thread_preempt_disable();
spinlock_lock_common(lock);
}
/*
* Unlock a spin lock.
*
* The spin lock must be locked, and must have been locked by the calling
* thread.
*
* This operation synchronizes with subsequent lock operations on the same
* spin lock.
*/
static inline void
spinlock_unlock(struct spinlock *lock)
{
spinlock_unlock_common(lock);
thread_preempt_enable();
}
/*
* Versions of the spinlock functions that also disable interrupts during
* critical sections.
*/
/*
* Attempt to lock the given spin lock.
*
* Return 0 on success, EBUSY if the spin lock is already locked.
*
* Interrupts are disabled on success, in which case the flags passed
* by the caller are filled with the previous value of the CPU flags.
*
* If the operation succeeds, prior unlock operations on the same spin lock
* synchronize with this operation.
*/
static inline int
spinlock_trylock_intr_save(struct spinlock *lock, unsigned long *flags)
{
int error;
thread_preempt_disable_intr_save(flags);
error = spinlock_lock_fast(lock);
if (unlikely(error)) {
thread_preempt_enable_intr_restore(*flags);
}
return error;
}
/*
* Lock a spin lock.
*
* If the spin lock is already locked, the calling thread spins until the
* spin lock is unlocked.
*
* A spin lock can only be locked once.
*
* This function disables interrupts. The flags passed by the caller are
* filled with the previous value of the CPU flags.
*
* Prior unlock operations on the same spin lock synchronize with this
* operation.
*/
static inline void
spinlock_lock_intr_save(struct spinlock *lock, unsigned long *flags)
{
thread_preempt_disable_intr_save(flags);
spinlock_lock_common(lock);
}
/*
* Unlock a spin lock.
*
* The spin lock must be locked, and must have been locked by the calling
* thread.
*
* The CPU flags, obtained from a locking operation, are restored.
*
* This operation synchronizes with subsequent lock operations on the same
* spin lock.
*/
static inline void
spinlock_unlock_intr_restore(struct spinlock *lock, unsigned long flags)
{
spinlock_unlock_common(lock);
thread_preempt_enable_intr_restore(flags);
}
/*
* This init operation provides :
* - uncontended spinlock locking
*
* Contended locking may only occur after starting APs.
*/
INIT_OP_DECLARE(spinlock_setup);
#endif /* KERN_SPINLOCK_H */
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