c - DEFINE_SPINLOCK(...) spinlock_t 参数错误

Question

我目前正在从事一个类项目，其中包括基于内核的信号量实现。而不是使用 DEFINE_SPINLOCK(sem_lock);作为/kernel/sys.c 中的全局变量，我创建了一个方案，其中信号量结构包含一个 spinlock_t 变量(在用户空间中被屏蔽为 void *)，以便让不同的信号量有机会向下()/向上( ) 独立(这应该转化为更高效的代码，等待更少)。我进行了一个系统调用来初始化一个信号量，将一个指针传递给该结构。但是，在初始化信号量的 spinlock_t 时，有一行出错。

我已经联系了我的教授，他说为了这个作业的目的，只是使用一个带有全局自旋锁定义的粗略实现。但是，很难放手。虽然我显然不介意走那条路，但我仍然想了解为什么我的实现不起作用。谁能帮我解决这个问题？

这是错误:

    CC      kernel/sys.o
kernel/sys.c: In function 'sys_cs1550_sem_init':
kernel/sys.c:2491: error: expected '=', ',', ';', 'asm' or '__attribute__' before '->' token
kernel/sys.c:2491: error: expected expression before '->' token
make[1]: *** [kernel/sys.o] Error 1
make: *** [kernel] Error 2

我试过以下方法:

DEFINE_SPINLOCK(sem->sem_lock);  
DEFINE_SPINLOCK(&(sem->sem_lock));  
DEFINE_SPINLOCK((&(sem->sem_lock)));  
DEFINE_SPINLOCK(*(sem->sem_lock));  
spinlock_t *lock = &(sem->sem_lock);  
DEFINE_SPINLOCK(lock);

我在/kernel/sys.c 中的信号量结构代码:

/*
* Initialize a semaphore with the creation of it's spinlock.
* The idea is to avoid having spinlocks in user space, by making
* the process as opaque as possible. Our lock is defined in the kernel as a spinlock_t,
* but as a void* in userspace. This allows us to have more than one semaphore as needed.
*/
struct cs1550_sem{
    spinlock_t *sem_lock;                   //The lock for our semaphore.
    int available_resources;                //Total # of available resources.
    struct cs1550_pnode *process_list;      //Pointer to the first node of our linked list.
};

我在/kernel/sys.c 中的信号量初始化系统调用代码:

asmlinkage long sys_cs1550_sem_init(struct cs1550_sem *sem, int resource_cap){
    DEFINE_SPINLOCK(sem->sem_lock);         //Define our lock.
    sem->process_list = NULL;               //Ensure we have a 'stopping point' when dequeueing.
    sem->available_resources = resource_cap;
    return 0;
}
EXPORT_SYMBOL_GPL(sys_cs1550_sem_init);

感谢您的宝贵时间。

Answer 1

你不能以那种方式使用这个宏。

// spinlock_types.h
#define DEFINE_SPINLOCK(x)      spinlock_t x = __SPIN_LOCK_UNLOCKED(x)

您的结构可能如下所示:

struct cs1550_sem{
    spinlock_t sem_lock;                   //The lock for our semaphore.
    int available_resources;                //Total # of available resources.
    struct cs1550_pnode *process_list;      //Pointer to the first node of our linked list.
};

和初始化:

asmlinkage long sys_cs1550_sem_init(struct cs1550_sem *sem, int resource_cap){
    spin_lock_init(&sem->sem_lock);         //Define our lock.
    sem->process_list = NULL;               //Ensure we have a 'stopping point' when dequeueing.
    sem->available_resources = resource_cap;
    return 0;
}

看看 https://www.kernel.org/doc/Documentation/spinlocks.txt 的第 3 课和 spin_lock_init(...) (第 295 行)