p.c

来自「虚地址空间基于文件OS内核源代码和文件」· C语言 代码 · 共 80 行

#include"kernel.h"

#define WRONG_THREAD_ID		-1
#define WRONG_SEMAPHORE_ID	-2
#define WRONG_THREAD_STATE	-3
#define WRONG_CAPABILITY	-4

int system_call_p(int thread_id,int semaphore_id,
	int sleep_flag,int v_flag,struct capability *cap)
{
	struct return_stack *rt;
	struct thread *t;
	struct process *pro;
	int return_value;
	int steps;

	if(semaphore_id==0){
		semaphore_id=os->thread[thread_id].semaphore;
		cap=&(os->semaphore[semaphore_id].capability);
	}
	return_value=p(thread_id,semaphore_id,sleep_flag,TRUE,cap);
	if(return_value<0)
		return return_value;
	if(!v_flag)
		return return_value;
	t=&(os->thread[thread_id]);
	rt=&(t->return_stack[t->return_stack_top-1]);
	if(rt->process_p_flag)
		return return_value;
	pro=&(os->process[rt->current_process]);
	if(pro->semaphore<=0)
		return return_value;
	steps=1;
	cap=&(os->semaphore[pro->semaphore].capability);
	if(system_call_v(pro->semaphore,&steps,cap)>=0)
		rt->process_p_flag=TRUE;
	return return_value;
}

int p(int thread_id,int semaphore_id,
	int sleep_flag,int result_flag,struct capability *cap)
{
	struct thread *t;
	struct semaphore *s;

	if((thread_id<0)||(thread_id>=THREAD_NUMBER))
		return(WRONG_THREAD_ID);
	t=&(os->thread[thread_id]);
	if((semaphore_id<0)||(semaphore_id>=SEMAPHORE_NUMBER))
		return WRONG_SEMAPHORE_ID;
	s=&(os->semaphore[semaphore_id]);
	if(s->process<0)
		return WRONG_SEMAPHORE_ID;
	if((t->state!=RUN)&&(t->state!=READY))
		return WRONG_THREAD_STATE;
	if(!KERNEL_COMPARE_CAPABILITY(s->capability,(*cap)))
		return WRONG_CAPABILITY;

	s->value--;
	if(s->value>=0) return 1;

	if(!sleep_flag)
		{s->value++;return 0;}
	if(s->thread_ring<0){
			t->sem_front=thread_id;
			t->sem_back=thread_id;
			s->thread_ring=thread_id;
		}
	else{
		t->sem_front=s->thread_ring;
		t->sem_back=os->thread[s->thread_ring].sem_back;
		os->thread[t->sem_front].sem_back=thread_id;
		os->thread[t->sem_back].sem_front=thread_id;
	}
	t->sleep_semaphore=semaphore_id;
	remove_from_heap(thread_id);
	t->set_v_operation_result_flag=result_flag;
	return 0;
}