/**
* down - acquire the semaphore
* @sem: the semaphore to be acquired
*
* Acquires the semaphore. If no more tasks are allowed to acquire the
* semaphore, calling this function will put the task to sleep until the
* semaphore is released.
*
* Use of this function is deprecated, please use down_interruptible() or
* down_killable() instead.
*/
void down(struct semaphore *sem)
{
unsigned long flags;
spin_lock_irqsave(&sem->lock, flags);
if (likely(sem->count > 0)){
sem->count--;
}else{
#ifdef CONFIG_MT_LOCK_DEBUG
if(sem->owner == current){
char aee_str[40];
printk("[Warning!Recursive Semaphore!][%d:%s], down:%s(0x%x)\n", current->pid, current->comm, sem->sem_name, sem);
sprintf( aee_str, "Recursive SemLock:%s\n", current->comm);
aee_kernel_warning( aee_str,"mtlock debugger\n");
dump_stack();
}
#endif
__down(sem);
}
#ifdef CONFIG_MT_LOCK_DEBUG
if(0 == sem->count)
sem_set_owner(sem);
#endif
spin_unlock_irqrestore(&sem->lock, flags);
}
void down(struct semaphore *sem)
{
unsigned long flags;
spin_lock_irqsave(&sem->lock, flags);
if (likely(sem->count > 0))
sem->count--;
else
__down(sem);
spin_unlock_irqrestore(&sem->lock, flags);
}
static int
usem_down(semaphore_t *sem, unsigned int timeout) {
unsigned long saved_ticks;
timer_t __timer, *timer = ipc_timer_init(timeout, &saved_ticks, &__timer);
uint32_t flags;
if ((flags = __down(sem, WT_USEM, timer)) == 0) {
return 0;
}
assert(flags == WT_INTERRUPTED);
return ipc_check_timeout(timeout, saved_ticks);
}
/**
* down: 获取信号量
* @sem: the semaphore to be acquired
*
* Acquires the semaphore. If no more tasks are allowed to acquire the
* semaphore, calling this function will put the task to sleep until the
* semaphore is released.
*
* Use of this function is deprecated, please use down_interruptible() or
* down_killable() instead.
*/
void down(struct semaphore *sem)
{
unsigned long flags;
spin_lock_irqsave(&sem->lock, flags);
/*count > 0 :进程直接获得信号量,减1返回*/
if (likely(sem->count > 0))
sem->count--;
else
__down(sem); /*count < 0,进程无法获得信号量,需要加入到等到队列中*/
spin_unlock_irqrestore(&sem->lock, flags);
}
void __sched
down(struct semaphore *sem)
{
#ifdef WAITQUEUE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
#ifdef CONFIG_DEBUG_SEMAPHORE
printk("%s(%d): down(%p) <count=%d> from %p\n",
current->comm, current->pid, sem,
atomic_read(&sem->count), __builtin_return_address(0));
#endif
__down(sem);
}
/**
* down - acquire the semaphore
* @sem: the semaphore to be acquired
*
* Acquires the semaphore. If no more tasks are allowed to acquire the
* semaphore, calling this function will put the task to sleep until the
* semaphore is released.
*
* Use of this function is deprecated, please use down_interruptible() or
* down_killable() instead.
*/
void down(struct semaphore *sem)
{
unsigned long flags;
raw_spin_lock_irqsave(&sem->lock, flags);
#ifdef CONFIG_ILOCKDEP
ilockdep_acquire(&sem->idep_map, _RET_IP_, (void *)sem);
#endif
if (likely(sem->count > 0))
sem->count--;
else
__down(sem);
#ifdef CONFIG_ILOCKDEP
ilockdep_acquired(&sem->idep_map, _RET_IP_, (void *)sem);
#endif
raw_spin_unlock_irqrestore(&sem->lock, flags);
}
static void
usem_down(semaphore_t *sem) {
uint32_t flags = __down(sem, WT_USEM);
assert(flags == 0 || flags == WT_INTERRUPTED);
}
void
down(semaphore_t *sem) {
uint32_t flags = __down(sem, WT_KSEM);
assert(flags == 0);
}