Linux内核同步，历程，线程同步
日期：2014-05-16 浏览次数：20778 次
Linux内核同步，进程，线程同步
int mutex_lock_interruptible (struct mutex *lock);
Same, but can be interrupted. If interrupted, returns a non zero value and doesn't hold the lock.
Test the return value!!!
int mutex_trylock (struct mutex *lock);
Never waits. Returns a non zero value if the mutex is not available.int mutex_is_locked
(struct mutex *lock);Just tells whether the mutex is locked or not.
void mutex_unlock (struct mutex *lock);
Releases the lock. Make sure you do it as quickly as possible!
内核同步：
主要是防止多核处理器同时访问修改某段代码，或者在对设备驱动程序进行临界区保护。主要有一下几种方式：
1. Mutex（互斥）
头文件：
#include <linux/mutex.h>
初始化方法：
DEFINE_MUTEX(name);
或者
void mutex_init(struct mutex *lock);
使用方法：
void mutex_lock (struct mutex *lock);
尝试得到互斥量，否则进入睡眠，不能被中断，否则会导致进程无法杀死
int mutex_lock_interruptible (struct mutex *lock);
Same, but can be interrupted. If interrupted, returns a non zero value and doesn't hold the lock.
Test the return value!!!
可以被中断
int mutex_trylock (struct mutex *lock);
Never waits. Returns a non zero value if the mutex is not available.int mutex_is_locked
(struct mutex *lock);Just tells whether the mutex is locked or not.
无等待
void mutex_unlock (struct mutex *lock);
Releases the lock. Make sure you do it as quickly as possible!
2. Reader/writer semphopres 读写信号量
Allow shared access by unlimited readers, or by only 1 writer. Writers get priority.
允许有限数量的读访问，但是只能有一个写访问。
void init_rwsem (struct rw_semaphore *sem);
void down_read (struct rw_semaphore *sem);
int down_read_trylock (struct rw_semaphore *sem);
int up_read (struct rw_semaphore *sem);
void down_write (struct rw_semaphore *sem);
int down_write_trylock (struct rw_semaphore *sem);
int up_write (struct rw_semaphore *sem);
Well suited for rare writes, holding the semaphore briefly. Otherwise, readers get starved,
waiting too long for the semaphore to be released.
void init_rwsem (struct rw_semaphore *sem);
void down_read (struct rw_semaphore *sem);
int down_read_trylock (struct rw_semaphore *sem);
int up_read (struct rw_semaphore *sem);
void down_write (struct rw_semaphore *sem);
int down_write_trylock (struct rw_semaphore *sem);
int up_write (struct rw_semaphore *sem);
Well suited for rare writes, holding the semaphore briefly. Otherwise, readers get starved,
waiting too long for the semaphore to be released.
3. Spinlocks 自旋锁
初始化：
Static
spinlock_t my_lock = SPIN_LOCK_UNLOCKED;
Dynamic
void spin_lock_init (spinlock_t *lock);
spinlock_t my_lock = SPIN_LOCK_UNLOCKED;
Dynamic
void spin_lock_init (spinlock_t *lock);
使用：
void spin_[un]lock (spinlock_t *lock);
Doesn't disable interrupts. Used for locking in process context (critical sections in which you do not want to sleep).
void spin_lock_irqsave / spin_unlock_irqrestore (spinlock_t *lock, unsigned long flags);
Disables / restores IRQs on the loca
Doesn't disable interrupts. Used for locking in process context (critical sections in which you do not want to sleep).
void spin_lock_irqsave / spin_unlock_irqrestore (spinlock_t *lock, unsigned long flags);
Disables / restores IRQs on the loca
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