zircon/kernel/arch/x86/include/arch/spinlock.h

// Copyright 2016 The Fuchsia Authors
// Copyright (c) 2015 Travis Geiselbrecht
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT

#ifndef ZIRCON_KERNEL_ARCH_X86_INCLUDE_ARCH_SPINLOCK_H_
#define ZIRCON_KERNEL_ARCH_X86_INCLUDE_ARCH_SPINLOCK_H_

#include <lib/zircon-internal/thread_annotations.h>
#include <stdbool.h>
#include <zircon/compiler.h>

#include <arch/x86.h>
#include <arch/x86/mp.h>
#include <kernel/atomic.h>

__BEGIN_CDECLS

#define SPIN_LOCK_INITIAL_VALUE \
  (spin_lock_t) { 0 }

typedef struct TA_CAP("mutex") spin_lock {
  unsigned long value;
} spin_lock_t;

typedef x86_flags_t spin_lock_saved_state_t;
typedef uint spin_lock_save_flags_t;

void arch_spin_lock(spin_lock_t *lock) TA_ACQ(lock);
int arch_spin_trylock(spin_lock_t *lock) TA_TRY_ACQ(false, lock);
void arch_spin_unlock(spin_lock_t *lock) TA_REL(lock);

static inline uint arch_spin_lock_holder_cpu(spin_lock_t *lock) {
  return (uint)__atomic_load_n(&lock->value, __ATOMIC_RELAXED) - 1;
}

static inline bool arch_spin_lock_held(spin_lock_t *lock) {
  return arch_spin_lock_holder_cpu(lock) == arch_curr_cpu_num();
}

/* flags are unused on x86 */
#define ARCH_DEFAULT_SPIN_LOCK_FLAG_INTERRUPTS 0

static inline void arch_interrupt_save(spin_lock_saved_state_t *statep,
                                       spin_lock_save_flags_t flags) {
  *statep = x86_save_flags();
  __asm__ volatile("cli");
  atomic_signal_fence();
}

static inline void arch_interrupt_restore(spin_lock_saved_state_t old_state,
                                          spin_lock_save_flags_t flags) {
  x86_restore_flags(old_state);
}

__END_CDECLS

#endif  // ZIRCON_KERNEL_ARCH_X86_INCLUDE_ARCH_SPINLOCK_H_