你敢吗？抛砖引玉的问题，值得一看
路过的技术牛人，想请教一个问题。我想用fork产生3个子进程，分别执行不同的任务。并且给他们设定不同的优先级，让他们按照优先级执行。
我的代码在下面。进程1，child1的优先级是14.child2的优先级是10.child3的优先级是-3.按道理应该是子进程child3先执行。

#include<unistd.h>
#include<stdio.h>
#include<stdlib.h>
#include<sys/time.h>
#include<sys/resource.h>
#include<sys/types.h>


void main()
{
pid_t father,child1,child2,child3;
int prio;
father=getpid();
setpriority(PRIO_PROCESS,0,20);
//nice(10);
printf("the father ID is : %d\n",father);
prio=getpriority(PRIO_PROCESS,0);
printf("the father priority is %d\n",prio);
child1=fork();
if(child1==0) {
setpriority(PRIO_PROCESS,0,14);
prio=getpriority(PRIO_PROCESS,0);
printf("the child one ID is : %d\n",getpid());
printf("the child one priority is %d\n",prio);
}
else if(child1>0){
child2=fork();
if(child2==0) {
setpriority(PRIO_PROCESS,0,10);
prio=getpriority(PRIO_PROCESS,0);
printf("the child two ID is : %d\n",getpid());
printf("the child two priority is %d\n",prio);
}
else if(child2>0){
child3=fork();
if(child3==0) {
setpriority(PRIO_PROCESS,0,-3);
prio=getpriority(PRIO_PROCESS,0);
printf("the child three ID is : %d\n",getpid());
printf("the child three priority is %d\n",prio);
}
else if(child3>0) {
printf("my ID is %d\n",getpid());
printf("my prio is %d\n",getpriority(PRIO_PROCESS,0));
}

}
}

}

执行结果是：
先执行1，再 2，再3


[解决办法]

C/C++ code

#include<unistd.h>#include<stdio.h>#include<stdlib.h>#include<sys/time.h>#include<sys/resource.h>#include<sys/types.h>#include<sched.h>void main(){  pid_t father,child1,child2,child3;  int prio;  int rt,curr_policy;  struct sched_param my_params;  my_params.sched_priority=sched_get_priority_max(SCHED_RR);  father=getpid();  curr_policy=sched_getscheduler(father);  printf("SCHED_OTHER = %d SCHED_FIFO =%d SCHED_RR=%d \n",SCHED_OTHER,SCHED_FIFO,SCHED_RR);  printf("the current scheduler = %d \n",curr_policy);  rt=sched_setscheduler(0,SCHED_RR,&my_params);  if(rt<0)  {    perror("sched_setscheduler to SCHED_RR error");    exit(0);  }  curr_policy=sched_getscheduler(father);  printf("the current scheduler = %d \n",curr_policy);  //father=getpid();  setpriority(PRIO_PROCESS,0,20);  //nice(10);  printf("the father ID is : %d\n",father);  prio=getpriority(PRIO_PROCESS,0);  printf("the father priority is %d\n",prio);  child1=fork();  if(child1==0) {  curr_policy=sched_getscheduler(child1);  printf("child1 scheduler = %d \n",curr_policy);  setpriority(PRIO_PROCESS,0,14);  prio=getpriority(PRIO_PROCESS,0);  printf("the child one ID is : %d\n",getpid());  printf("the child one priority is %d\n",prio);  }  else if(child1>0){  child2=fork();  if(child2==0) {  curr_policy=sched_getscheduler(child2);  printf("child2 scheduler = %d \n",curr_policy);  setpriority(PRIO_PROCESS,0,10);  prio=getpriority(PRIO_PROCESS,0);  printf("the child two ID is : %d\n",getpid());  printf("the child two priority is %d\n",prio);  }  else if(child2>0){  child3=fork();  if(child3==0) {  curr_policy=sched_getscheduler(child3);  printf("child2 scheduler = %d \n",curr_policy);  setpriority(PRIO_PROCESS,0,-3);  prio=getpriority(PRIO_PROCESS,0);  printf("the child three ID is : %d\n",getpid());  printf("the child three priority is %d\n",prio);  }  else if(child3>0) {  printf("my ID is %d\n",getpid());  printf("my prio is %d\n",getpriority(PRIO_PROCESS,0));  }     }  }}