1 #include <common/spinlock.h>
2 #include <process/preempt.h>
3 
__arch_spin_lock(spinlock_t * lock)4 void __arch_spin_lock(spinlock_t *lock)
5 {
6     __asm__ __volatile__("1:    \n\t"
7                          "lock decb %0   \n\t" // 尝试-1
8                          "jns 3f    \n\t"      // 加锁成功，跳转到步骤3
9                          "2:    \n\t"          // 加锁失败，稍后再试
10                          "pause \n\t"
11                          "cmpb $0, %0   \n\t"
12                          "jle   2b  \n\t" // 若锁被占用，则继续重试
13                          "jmp 1b    \n\t" // 尝试加锁
14                          "3:"
15                          : "=m"(lock->lock)::"memory");
16     preempt_disable();
17 }
18 
__arch_spin_unlock(spinlock_t * lock)19 void __arch_spin_unlock(spinlock_t *lock)
20 {
21     preempt_enable();
22     __asm__ __volatile__("movb $1, %0   \n\t" : "=m"(lock->lock)::"memory");
23 }
24 
__arch_spin_lock_no_preempt(spinlock_t * lock)25 void __arch_spin_lock_no_preempt(spinlock_t *lock)
26 {
27     __asm__ __volatile__("1:    \n\t"
28                          "lock decb %0   \n\t" // 尝试-1
29                          "jns 3f    \n\t"      // 加锁成功，跳转到步骤3
30                          "2:    \n\t"          // 加锁失败，稍后再试
31                          "pause \n\t"
32                          "cmpb $0, %0   \n\t"
33                          "jle   2b  \n\t" // 若锁被占用，则继续重试
34                          "jmp 1b    \n\t" // 尝试加锁
35                          "3:"
36                          : "=m"(lock->lock)::"memory");
37 }
38 
__arch_spin_unlock_no_preempt(spinlock_t * lock)39 void __arch_spin_unlock_no_preempt(spinlock_t *lock)
40 {
41     __asm__ __volatile__("movb $1, %0   \n\t" : "=m"(lock->lock)::"memory");
42 }
43 
__arch_spin_trylock(spinlock_t * lock)44 long __arch_spin_trylock(spinlock_t *lock)
45 {
46     uint64_t tmp_val = 0;
47     preempt_disable();
48     // 交换tmp_val和lock的值，若tmp_val==1则证明加锁成功
49     asm volatile("lock xchg %%bx, %1  \n\t" // 确保只有1个进程能得到锁
50                  : "=q"(tmp_val), "=m"(lock->lock)
51                  : "b"(0)
52                  : "memory");
53     if (!tmp_val)
54         preempt_enable();
55     return tmp_val;
56 }