mutex_lock 函数分析

path：kernel/locking/mutex.c

function source code:

void __sched mutex_lock(struct mutex *lock)
{
    might_sleep();

    if (!__mutex_trylock_fast(lock))
        __mutex_lock_slowpath(lock);
}
EXPORT_SYMBOL(mutex_lock);

从上面代码可以看出 mutex_lock 函数有两条路径，首先尝试__mutex_trylock_fast(lock) 快速路径，如果尝试失败就进入 __mutex_lock_slowpath(lock) 慢速路径

__mutex_trylock_fast(lock)
        atomic_long_try_cmpxchg_acquire(&lock->owner, &zero, curr)  //判断 curr 的值是否 小于等于 zero
                arch_atomic_long_try_cmpxchg_acquire(v, old, new);
                        arch_atomic_try_cmpxchg_acquire(v, (int *)old, new);
                                arch_atomic_try_cmpxchg_acquire(atomic_t *v, int *old, int new)

判断curr 的值是否小于等于 0 如果小于等于 0 则进入 __mutex_lock_slowpath(lock) 否则就直接返回

__mutex_lock_slowpath(lock)
        __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, false);

__mutex_lock_slowpath(lock) 锁定互斥锁 ，可能会中断