Semaphore parsing in Linux kernel

Semaphore in the Linux kernel is a common method to protect critical zones using the kernel. the kernel semaphores are the same in terms of concept and principle, and are different from user-state semaphores, but it cannot be used outside the kernel. the kernel semaphore is actually a sleep lock prototype:/* Pleasedo...
Semaphore in the Linux kernel is a common method to protect critical zones using the kernel. the kernel semaphores are the same in terms of concept and principle, and are different from user-state semaphores, but it cannot be used outside the kernel. the kernel semaphore is actually a prototype of a sleep lock:/* Please don't access any members of this structure directly */struct semaphore {spinlock_t lock; unsigned int count; struct list_head wait_list;}; www.2cto.com instance: Ibmphp_hpc.c (\ linux-2.6.30.4 \ drivers \ pci \ hotplug) 1 declare static struct semaphore semOperations; // lock all operations and 2 is initialized in the void function _ Init ibmphp_hpc_initvars (void) init_MUTEX (& semOperations); other initialization methods initialize semaphores sema_init (struct semaphore * sem, int val); used to initialize semaphores, semaphores, set the semaphores sem value to val init_MUTEX (struct semaphore * sem). it is used to initialize the semaphores and set the semaphores sem value to 1 init_MUTEX_LOCKED (struct semaphore * sem ); this parameter is used to initialize the number and set the semaphores sem value to 0, that is, DECLARE_MUTEX (name). It defines a semaphores named name, and initialize the semaphores to 1 3. use the function void ibmphp_lock_operations (void) in www.2cto.com down (& semOper By using the down operation semaphores may cause the calling process to sleep until the semaphores are released by other callers, waiting is in the D state (which can be viewed in top). If you do not want to call the process to sleep, you should use down_trylock (& semOperations). how many threads can this number be obtained? ㄐ PA? Em; if yes? P gets, and it gets the Semaphore and? Return 0; otherwise ,? A non-zero value is returned. it does not cause sleep of the caller. you can use int down_interruptible (struct semaphore * sem) in the interrupt context if you want the caller to be interrupted ); this function is used to obtain semaphores sem. if semaphores are unavailable, the process is set to TASK_INTERRUPTIBLE. the number of sleep tasks is determined by the return value to determine whether the returned results are normal or interrupted. if 0 is returned, it indicates that the semaphore is returned normally. if the return value is not 0, it indicates that the semaphore is interrupted. 4. release void ibmphp_unlock_operations (void) {debug ("% s-Entry \ n ", _ func _); up (& semOperations); to_debug = 0; debug ("% s-Exit \ n", _ func __);} this number releases the semaphores sem. in essence, the sem value is increased by 1. if the sem value is not a positive number, it indicates that a task is waiting for the semaphores. Therefore, you need to wake up the waiting person www.2cto.com. note: the down Series function will reduce the semaphore value by 1 up, and add the semaphore value to the author tsuibin.