fork(3) download 
  1. #include <pthread.h>
  2. #include <unistd.h>
  3. #include <stdio.h>
  4. #include <time.h>
  5.  
  6.  
  7. #define PID_MIN  	0
  8. #define PID_MAX 	3
  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[PID_MAX-PID_MIN+1];
  23. int thread_counter =0;
  24.  
  25.  
  26. int allocate_map(void);
  27. int allocate_pid(void);
  28. void release_pid(int pid);
  29.  
  30.  
  31.  // Allocates the pid map.
  32.  
  33. int allocate_map(void) 
  34. {
  35. 	/*initilize to zero explicitly just to make sure*/
  36. 	int i;
  37. 	for (i =0;i<PID_MAX-PID_MIN+1;i++)
  38. 	{
  39. 		pid_map[i] = 0;
  40. 		S++;
  41.  
  42. 	}
  43. 	printf("map allocated!S=%d\n",S);
  44. 	return 1;
  45. }
  46.  
  47. /**
  48.  * Allocates a pid
  49.  */
  50. int allocate_pid(void)
  51. {
  52. 	int next_pid;
  53. 	int i;
  54. 	while (S<=0)
  55. 	{}
  56.  
  57. 	pthread_mutex_lock(&mutex);
  58. 	S--;
  59. 	for (i =0;i<PID_MAX-PID_MIN;i++)
  60. 		{
  61. 			if (pid_map[i] == 0)
  62. 				{
  63. 					pid_map[i] = 1;
  64. 					next_pid=i;
  65. 					pthread_mutex_unlock(&mutex);
  66. 					return next_pid+PID_MIN;
  67.  
  68.  
  69.  
  70. 				}
  71. 		}
  72.  
  73.  
  74. }
  75. /**
  76.  * Releases a pid
  77.  */
  78. void release_pid(int pid)
  79. {
  80. 	pid = pid-PID_MIN;
  81. 	pid_map[pid] = 0;
  82. 	S++;
  83. }
  84.  
  85. void *do_something(void *threadid)
  86. 	{
  87. 		int  my_pid;
  88. 		long thread_id;
  89. 		int i;
  90. 		double r;
  91. 		thread_id= (long)threadid;
  92.  
  93. 		for (i=0;i<ITERATIONS;i++)
  94. 		{
  95. 			r = rand()%50; // 0-50
  96. 			r=r/10;
  97. 			//r=0.1;
  98. 			//printf("thread %d trying to allocate PID..., S=%d\n",thread_id,S);
  99. 			my_pid=allocate_pid();
  100.  
  101. 			printf("Thread number %d got PID %d S=%d\n", thread_id, my_pid,S);
  102. 			sleep(r);
  103. 			release_pid(my_pid);
  104. 			printf("Thread number %d released PID %d S=%d \n", thread_id, my_pid,S);
  105. 		}
  106. 		thread_counter--;
  107. 		pthread_exit(NULL);
  108. 	}
  109.  
  110.  
  111. void main()
  112. {
  113. 	int i,rc;
  114. 	time_t t;
  115. 	pthread_t tid[NUM_THREADS];
  116. 	srand((unsigned) time(&t));
  117. 	allocate_map();
  118. 	for (i =0;i<10;i++)
  119. 	{
  120. 		//printf("In main: creating thread %d S=%d\n", i,S);
  121. 		thread_counter++;
  122. 		rc=pthread_create(&tid[i], NULL, do_something, (void *)i);
  123.  
  124. 	}
  125. 	while (thread_counter >0)
  126. 	{
  127. 		sleep(1);
  128. 	}
  129. 	printf("DONE!\n");
  130. }
  131.  
  132.  
  133.  
  134.  
Time limit exceeded #stdin #stdout 5s 84224KB
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https://ideone.com/NaFOvO
language:
C (gcc 8.3)
created:
9 years ago
visibility:
public

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