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我是 C 新手，我只是想运行 Pacheco 的书“并行编程简介”中的这段代码。而且我只是不知道应该如何在main(). 是&semaphores[dest]和&semaphores[my_rank]数组吗？

C代码：

/* messages is allocated and initialized to NULL in main */
/* semaphores is allocated and initialized to 0 (locked) in main */
void *Send_msg(void* rank) {
    long my_rank = (long) rank;
    long dest = (my_rank + 1) % thread_count;
    char* my_msg = (char*)malloc(MSG_MAX*sizeof(char));

    sprintf(my_msg, "Hello to %ld from %ld", dest, my_rank);
    messages[dest] = my_msg;
    sem_post(&semaphores[dest])
    /* ‘‘Unlock’’ the semaphore of dest */

    sem_wait(&semaphores[my_rank]);/* Wait for our semaphore to be unlocked */
    printf("Thread %ld > %s\n", my_rank, messages[my_rank]);

    return NULL;
} /* Send_msg */

当我试图将输出数组写入文件时，我想实现这种类型的顺序机制。这是我的代码：

int k = 0;
long dest = (my_rank + 1) % THREAD_COUNT;

if(genCount%50==0){
//incrementing file name

//semapthore lock
sem_post(&semaphores[dest]);

sem_wait(&semaphores[my_rank]);

snprintf(buffer, sizeof(char) * 32, "file%i.dat", k);

//open the file
fp = fopen(buffer, "r+");
if (fp == NULL) {
  printf("I couldn't open file for writing.\n");
  exit(0);
}

int loop1, loop2;

//outputting the array into the file
for (loop1 = my_first_i; loop1 < my_last_i; loop1++){
  for(loop2 = my_first_i; loop2 < my_last_i; loop2++){
fprintf(fp,"%d\t", map[loop1][loop2]);
  }
}

//close the file
fclose(fp);

k++;

}

信号量的初始化main()：

  int semCount;
  for(semCount = 0; semCount < THREAD_COUNT; semCount++){
   sem_init(&semaphores[semCount], 0, 1);
  }

我也有它作为一个全局变量：

#define THREAD_COUNT 4
sem_t semaphores[THREAD_COUNT];

该程序编译，但它给了我这个错误：

      *** Error in `./ebola_serial': double free or corruption (out): 0x00007f49700008c0 ***
  *** Error in `======= Backtrace: =========
  /lib64/libc.so.6(+0x7238e)[0x7f49868f038e]
  ./ebola_serial/lib64/libc.so.6(+0x7a0c8)[0x7f49868f80c8]
  ': /lib64/libc.so.6(cfree+0x48)[0x7f49868fb798]
  double free or corruption (out)/lib64/libc.so.6(fclose+0x113)[0x7f49868e6473]
  ./ebola_serial[0x401717]
  /lib64/libpthread.so.0(+0x75bd)[0x7f4986c395bd]
  : 0x/lib64/libc.so.6(clone+0x6d)[0x7f498697562d]
  ======= Memory map: ========
  00007f49700008c000400000-00402000 r-xp 00000000 08:01 802698                             /home/name/Desktop/try ca/ebola_serial
  00601000-00602000 r--p 00001000 08:01 802698                             /home/name/Desktop/try ca/ebola_serial
  00602000-00603000 rw-p 00002000 08:01 802698                             /home/name/Desktop/try ca/ebola_serial
  00603000-009d3000 rw-p 00000000 00:00 0 
  01b96000-01bb7000 rw-p 00000000 00:00 0                                  [heap]
  7f4970000000-7f4970021000 rw-p 00000000 00:00 0 
  7f4970021000-7f4974000000 ---p 00000000 00:00 0 
  7f4978000000-7f4978021000 rw-p 00000000 00:00 0 
  7f4978021000-7f497c000000 ---p 00000000 00:00 0 
  7f497c000000-7f497c021000 rw-p 00000000 00:00 0 
  7f497c021000-7f4980000000 ---p 00000000 00:00 0 
  7f4980000000-7f4980021000 rw-p 00000000 00:00 0 
  7f4980021000-7f4984000000 ---p 00000000 00:00 0 
  7f4984663000-7f4984679000 r-xp 00000000 08:01 131531                     /usr/lib64/libgcc_s-4.9.2.so.1
  7f4984679000-7f4984878000 ---p 00016000 08:01 131531                     /usr/lib64/libgcc_s-4.9.2.so.1
  7f4984878000-7f4984879000 r--p 00015000 08:01 131531                     /usr/lib64/libgcc_s-4.9.2.so.1
  7f4984879000-7f498487a000 rw-p 00016000 08:01 131531                     /usr/lib64/libgcc_s-4.9.2.so.1
  7f498487a000-7f498487b000 ---p 00000000 00:00 0 
  7f498487b000-7f498507b000 rw-p 00000000 00:00 0                          [stack:7376]
  7f498507b000-7f498507c000 ---p 00000000 00:00 0 
  7f498507c000-7f498587c000 rw-p 00000000 00:00 0 
  7f498587c000-7f498587d000 ---p 00000000 00:00 0 
  7f498587d000-7f498607d000 rw-p 00000000 00:00 0                          [stack:7374]
  7f498607d000-7f498607e000 ---p 00000000 00:00 0 
  7f498607e000-7f498687e000 rw-p 00000000 00:00 0                          [stack:7373]
  7f498687e000-7f4986a28000 r-xp 00000000 08:01 130947                     /usr/lib64/libc-2.20.so
  7f4986a28000-7f4986c28000 ---p 001aa000 08:01 130947                     /usr/lib64/libc-2.20.so
  7f4986c28000-7f4986c2c000 r--p 001aa000 08:01 130947                     /usr/lib64/libc-2.20.so
  7f4986c2c000-7f4986c2e000 rw-p 001ae000 08:01 130947                     /usr/lib64/libc-2.20.so
  7f4986c2e000-7f4986c32000 rw-p 00000000 00:00 0 
  7f4986c32000-7f4986c49000 r-xp 00000000 08:01 130973                     /usr/lib64/libpthread-2.20.so
  7f4986c49000-7f4986e48000 ---p 00017000 08:01 130973                     /usr/lib64/libpthread-2.20.so
  7f4986e48000-7f4986e49000 r--p 00016000 08:01 130973                     /usr/lib64/libpthread-2.20.so
  7f4986e49000-7f4986e4a000 rw-p 00017000 08:01 130973                     /usr/lib64/libpthread-2.20.so
  7f4986e4a000-7f4986e4e000 rw-p 00000000 00:00 0 
  7f4986e4e000-7f4986f53000 r-xp 00000000 08:01 130955                     /usr/lib64/libm-2.20.so
  7f4986f53000-7f4987152000 ---p 00105000 08:01 130955                     /usr/lib64/libm-2.20.so
  7f4987152000-7f4987153000 r--p 00104000 08:01 130955                     /usr/lib64/libm-2.20.so
  7f4987153000-7f4987154000 rw-p 00105000 08:01 130955                     /usr/lib64/libm-2.20.so
  7f4987154000-7f4987174000 r-xp 00000000 08:01 130940                     /usr/lib64/ld-2.20.so
  7f4987353000-7f4987356000 rw-p 00000000 00:00 0 
  7f498736d000-7f4987373000 rw-p 00000000 00:00 0 
  7f4987373000-7f4987374000 r--p 0001f000 08:01 130940                     /usr/lib64/ld-2.20.so
  7f4987374000-7f4987376000 rw-p 00020000 08:01 130940                     /usr/lib64/ld-2.20.so
  7ffce31e3000-7ffce3205000 rw-p 00000000 00:00 0                          [stack]
  7ffce320d000-7ffce320f000 r--p 00000000 00:00 0                          [vvar]
  7ffce320f000-7ffce3211000 r-xp 00000000 00:00 0                          [vdso]
  ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
  Aborted

任何帮助，将不胜感激。

4

1 回答 1

2

看起来像这样定义的信号量

sem_t semaphores[N];

其中 N 是信号量的数量

为了初始化信号量，您应该使用 sem_init 函数，它接受一个指向所需信号量的指针，一个启用共享进程使用的标志和信号量的初始值。

sem_init(&semaphores[0], 0, 1);

在您的情况下，信号量实例存储在称为信号量的数组中，因此您必须迭代数组的所有成员才能初始化

int i;
for(i=0;i<N;i++)
    sem_init(&semaphores[i], 0, 1);

Finlay 使用信号量必须以这种方式调用 sem_wait 和 sem_post 函数

sem_wait(&semaphores[0 to N-1]); // Locking semaphore
sem_post(&semaphores[0 to N-1]); // Unlocking it
于 2016-12-14T14:21:51.403 回答