we developed a set of system V semphore interface for our application, in general, all of them work normal, seldom cause the deadlock. Here are some important sem_wait and sem_post interface, pls point some suggestion to fixed the deadlock problem:
int sem_wait_V(int id, struct sembuf *sem_pv)
{
sem_pv = new struct sembuf [1] ;
if (sem_op(id,-1, sem_pv)<0)
{
delete sem_pv ;
return -1;
}
delete sem_pv ;
return 0;
}
int sem_post_V(int id, int sem_post_value_V, struct sembuf *sem_pv)
{
if ((sem_post_value_V = semctl(id,0,GETVAL,0)) <0)
{
return -1;
}
if( sem_post_value_V > SEM_POST_LIMIT )
{
if( sem_post_value_V == SEM_POST_LIMIT + 1 ) return -1 ;
return -1 ;
}
sem_pv = new struct sembuf [1] ;
if (sem_op(id,1,sem_pv)<0)
{
delete sem_pv ;
return -1;
}
delete sem_pv ;
return 0;
}
int sem_op(int id,int value, struct sembuf sem_pv[1] )
{
int sem_value ,sem_value1;
sem_pv[0].sem_num = 0 ;
sem_pv[0].sem_flg = 0 ;
if ((sem_pv[0].sem_op =value) == 0)
{
printf("sem_op error: operator is zero !!!!!!!(%d)\n",id) ;
return -1;
}
if ((sem_value = semctl(id,0,GETVAL,0)) <0)
{
perror("semctl create GETVAL");
return -1;
}
again:;
if (semop(id,&sem_pv[0],1)<0)
{
sched_yield() ;
if(errno==EINTR)
{
if ((sem_value1 = semctl(id,0,GETVAL,0)) <0)
{
perror("semctl create GETVAL");
return -1;
}
else
{
if (sem_value != sem_value1 )
return -1;
else
goto again;
}
}
return -1;
}
return 1;
}