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  1. #include <pthread.h>
  2. #include <unistd.h>
  3. #include <stdio.h>
  4. #include <time.h>
  5.  
  6.  
  7. #define PID_MIN  	300
  8. #define PID_MAX 	350
  9.  
  10. #define NUM_THREADS 100
  11. #define ITERATIONS	10
  12. #define SLEEP		5
  13.  
  14.  
  15.  
  16.  
  17. int S;
  18.  
  19. /* mutex lock for accessing pid_map */
  20. pthread_mutex_t mutex;
  21.  
  22. int* pid_map;
  23. int thread_counter =0;
  24.  
  25.  
  26. int allocate_map(void);
  27. int allocate_PID(int thread_id); //not (void) purely for a nicer output, it shows therad id
  28. void release_pid(int pid);
  29.  
  30.  
  31.  
  32.  // Allocates the pid map.
  33.  
  34. int allocate_map(void) 
  35. {
  36. 	/*initilize to zero explicitly just to make sure*/
  37. 	int i;
  38. 		pid_map =(int*)malloc((PID_MAX-PID_MIN+1)*sizeof(int));
  39. 		if (pid_map == NULL)
  40. 			return -1;
  41.  
  42. 		// the structure is a bitmap:
  43. 		//0 - available,
  44. 		//1 - taken
  45.         for (i =0;i<PID_MAX-PID_MIN+1;i++)
  46.         {
  47.             pid_map[i] = 0;
  48.             S++;
  49.  
  50.         }
  51.         printf("map allocated!S=%d\n",S);
  52.         return 1;
  53.  
  54. }
  55.  
  56. /**
  57.  * Allocates a pid
  58.  */
  59. int allocate_PID(int t_id)
  60. {
  61. 	int next_pid;
  62. 	int i,j;
  63. 	int err;
  64.  
  65. 	if (S<=0)
  66. 		return -1; //NOT thread SAFE
  67.  
  68.     pthread_mutex_lock(&mutex);
  69. 	while (S<=0)
  70.     {}
  71.  
  72. 	for (i =0;i<PID_MAX-PID_MIN+1;i++)
  73. 		{
  74. 			if (pid_map[i] == 0)
  75. 				{
  76.  
  77.                     S--;
  78.                     printf("Thread number %d got PID %d S=%d\n", t_id, i+PID_MIN,S);
  79.                     pid_map[i] = 1;
  80. 					next_pid=i;
  81. 					pthread_mutex_unlock(&mutex);
  82. 					return (next_pid+PID_MIN);
  83.  
  84.  
  85.  
  86. 				}
  87. 		}
  88. 	//for debug purposes:
  89. 	//if a thread will pass mutex and S-semaphore
  90. 	//but won't find a PID then -999 will be returned
  91. 	return -999;
  92.  
  93. }
  94. /**
  95.  * Releases a pid
  96.  */
  97. void release_pid(int pid)
  98. {
  99. 	pid = pid-PID_MIN;
  100. 	pid_map[pid] = 0;
  101. 	S++;
  102. }
  103.  
  104. void *do_something(void *threadid)
  105. 	{
  106. 		int  my_pid;
  107. 		long thread_id;
  108. 		int i;
  109. 		double r;
  110. 		thread_id= (long)threadid;
  111. 		//printf("\nthread %d launched do_something\n", thread_id);
  112.  
  113.  
  114.  
  115. 		//for (i=0;i<10;i++)
  116. 		while(2>1)	
  117. 		{
  118. 			r = rand()%50; // 0-50
  119. 			r=r/10;
  120.  
  121. 			sleep(r/100);
  122. 			my_pid=allocate_PID(thread_id); //will return PID or "-1" if unsucessfull
  123. 			if (my_pid==-1)
  124. 				{
  125. 					printf("thread %d was NOT able allocate PID\n",thread_id);	
  126.  
  127. 				}
  128. 			else
  129. 				{
  130. 					sleep(r);
  131. 					release_pid(my_pid);
  132.  
  133. 					printf("Thread number %d released PID %d \tPIDs available: %d \n", thread_id, my_pid,S);
  134. 					thread_counter--;
  135. 					return;
  136. 				}
  137. 		}
  138.  
  139.  
  140. 	}
  141.  
  142.  
  143. int main()
  144. {
  145. 	int i,err;
  146. 	time_t t;
  147.  
  148. 	pthread_t tid[NUM_THREADS];
  149. 	if (pthread_mutex_init(&mutex, NULL) != 0)
  150.     {
  151.         printf("\n mutex init failed\n");
  152.         return 1;
  153.     }
  154.  
  155.  
  156. 	srand((unsigned) time(&t));
  157. 	allocate_map();
  158. 	while(i < NUM_THREADS)
  159.     {
  160.         err = pthread_create(&(tid[i]), NULL, &do_something, (void*)i);
  161.         if (err != 0)
  162.             printf("\ncan't create thread :[%s]", strerror(err));
  163.         i++;
  164. 		thread_counter++;
  165. 		//printf("\nthread %d created\n", i);
  166.     }
  167.  
  168. 	while (thread_counter >0)
  169. 	{
  170. 		sleep(1);
  171. 	}
  172. 	 pthread_mutex_destroy(&mutex);
  173. 	printf("***DONE!***\n");
  174. }
  175.  
  176.  
  177.  
  178.  
Time limit exceeded #stdin #stdout 5s 133376KB
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stdout
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map allocated!S=51

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https://ideone.com/KuTw1F
language:
C (gcc 8.3)
created:
8 years ago
visibility:
public

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