semaaa

#include <linux/kernel.h>
#include <linux/syscalls.h>

#define MY_SYSLOG 351
#define MY_QUEUEEMPTY 352
#define MY_ENQUEUE 353
#define MY_DEQUEUE 354
#define MY_MONITOR 355


#define MONITOR_DOWN 0
#define MONITOR_UP 1
#define MONITOR_ENTER 2
#define MONITOR_LEAVE 3
#define MONITOR_WAIT 4
#define MONITOR_NOTIFY 5
#define MONITOR_NOTIFY_ALL 6
#define MONITOR_INIT 7
#define QUEUE_SIZE 16
static int read,write;
static char buf[QUEUE_SIZE];
static DEFINE_SEMAPHORE(lock_sema)
struct semaphore wait_sema = __SEMAPHORE_INITIALIZER(wait_sema, 0);
asmlinkage long sys_my_syslog(const char *test){

    printk(KERN_ALERT "Called with string: %s\n",test);

    return 0;
}



asmlinkage long sys_my_queueempty(){
      return(read==write);
}


asmlinkage long sys_my_queuefull(){
return ((write+1)%QUEUE_SIZE==read);
}


asmlinkage long sys_my_enqueue(char ch){
       if(sys_my_queuefull()){
        return -1;
      }else{
       write++;
       buf[write%QUEUE_SIZE]=ch;
       return 0;
      }
}

asmlinkage long sys_my_dequeue(){
      char ch;

      if(sys_my_queueempty())
       return -1;


       ch=buf[read%QUEUE_SIZE];
       read++;
       return (long)ch;
       }



/*semaphore lock_sema;
semaphore wait_sema;*/
int wait_count=0;
asmlinkage long sys_my_monitor(unsigned long op)
{
        int result ;
        printk( KERN_DEBUG "my_monitor: entered") ;
        switch(op){
        case MONITOR_DOWN:
                printk( KERN_DEBUG "my_monitor: MONITOR_DOWN") ;
                result = down_interruptible(&lock_sema) ;
                break ;
        case MONITOR_UP:
                printk( KERN_DEBUG "my_monitor: MONITOR_UP") ;
                up(&lock_sema) ;
                break ;
        case MONITOR_INIT:
              lock_sema unlocked (1);
              wait_sema locked (0);
              wait_count =0;
              break;
        case MONITOR_ENTER:
            result= down_interruptible(&lock_sema);
             break;
        case MONOTOR_LEAVE:
             up(&lock_sema) ;
             break;
        case MONITOR_WAIT:
             wait_count++;
             up(&lock_sema);
             result=down_interruptible(&wait_sema);
             result=down_interruptible(&lock_sema);
             break;
        case MONITOR_NOTIFY:
             if(wait_count>0){
             wait_count--;
             up(&wait_sema);
             }
             break;
       case MONITOR_NOTIFY_ALL:
            while(wait_count>0){
            wait_count--;
            up(&wait_sema);
            }
            break;
        default:
             printk( KERN_DEBUG "my_monitor: operation action") ;
        }
        return 0 ;
  }