PThread Mutex Lock & Unlock on Stack

Question

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#define NUM_THREADS     2
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
char **AddToStack(char *buffer)
{
  static char **stack = NULL;
  int stacksize = 0;
  if (buffer == NULL)
    return stack;
  if (stack == NULL){
    stack = calloc(1, sizeof(char*));
  }
  stack[stacksize] = strdup(buffer);
  stacksize++;
  stack = realloc(stack, (stacksize+1) * sizeof(char*));
  stack[stacksize] = NULL;
  return stack;
}
void *FRead(void *threadid)
{
pthread_mutex_lock(&mutex);
  char fname[256], buffer[256];
  FILE *ifile;
  long tid;
  int counter;
  tid = (long)threadid;
  sprintf(fname, "data%ld", tid);
  if ((ifile = fopen(fname, "r")) == NULL){
    printf("Error: Thread #%ld was unable to open file %s!n", tid, fname);
  }
  else{
    printf("Thread #%ld starting to read from file %s!n", tid, fname);
    fscanf(ifile, "%s", buffer);
    counter = 0;
 while (!feof(ifile)){
//pthread_mutex_lock(&mutex);  
    counter++;
      AddToStack(buffer);
      fscanf(ifile, "%s", buffer);
//pthread_mutex_unlock(&mutex);
    }
    fclose(ifile);
    printf("Thread #%ld added %d entries to the stack!n", tid, counter);
pthread_mutex_unlock(&mutex);
    pthread_exit(NULL);
  }
  return NULL;
}
int main(int argc, char *argv[])
{
  pthread_t threads[NUM_THREADS];
  int rc, i = 0;
  long t;
  char **stack;
  FILE *ofile;
  for(t=0;t<NUM_THREADS;t++){
    printf("In main: creating thread %ldn", t);
    rc = pthread_create(&threads[t], NULL, FRead, (void *)t);
    if (rc){
      printf("ERROR; return code from pthread_create() is %dn", rc);
      exit(-1);
    }
  }

for(t=0;t<NUM_THREADS;t++)
{
//pthread_join(threads[t],NULL);
}

  //Lets write the content of the stack into a file
  stack = AddToStack(NULL); //Get the base of the stack pointer
  if (stack != NULL){
    ofile = fopen("result.dat", "w");
    for (i = 0; stack[i] != NULL; i++)
      fprintf(ofile, "%sn", stack[i]);
    fclose(ofile);
  }
  fprintf(stderr, "%d data written to file result.datn", i);
  pthread_exit(NULL);
  return 0;
}

这是我的数据1和数据2文件

数据1： 放弃 降低 自卑 阿巴斯 使困窘 羞愧 阿巴什斯 唠叨 阿贝辛 减少 减弱 减少 减少 减轻 屠宰场 修道院 阿伯特 缩写 缩写 缩略语 缩略语 缩写 缩写 辞职 退位 退位 退位 腹部 绑架 绑架

数据2 ：

God
I
I'll
I'm
I've
Miss
Worry
a
ability
able
aboard
about
above
abroad
absence
absent
absolute
accident
accidentally
according
accordingly
account
acquaintance
across
act
action
active
activity
actual
admiration
admission
adress
advance
advantage
adventure

上面是我的互斥代码，但我想知道为什么我只能将 1 个数据写入文件结果.dat

这是我的输出

1 个数据写入文件结果.dat

Answer 1

首先，pthread_mutex_unlock(&mutex);pthread_exit(NULL);位置不正确。将此放在语句return NULL之前。

代码中有几个错误。请在下面找到更新的代码。

    #include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define NUM_THREADS     2
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
char **AddToStack(char *buffer)
{
  static char **stack = NULL;
  static int stacksize = 0;
  if (buffer == NULL)
    return stack;
  if (stack == NULL){
    stack = (char**)calloc(1, sizeof(char*));
  }
  stack[stacksize] = strdup(buffer);
  stacksize++;
  stack = (char**)realloc(stack, (stacksize+1) * sizeof(char*));
  stack[stacksize] = NULL;
  return stack;
}
void *FRead(void *threadid)
{
  pthread_mutex_lock(&mutex);
  char fname[256], buffer[256];
  FILE *ifile;
  long tid;
  int counter;
  tid = (long)threadid;
  sprintf(fname, "data%ld", tid);
  if ((ifile = fopen(fname, "r")) == NULL){
    printf("Error: Thread #%ld was unable to open file %s!n", tid, fname);
  }
  else{
    printf("Thread #%ld starting to read from file %s!n", tid, fname);
    fscanf(ifile, "%s", buffer);
    counter = 0;
    while (!feof(ifile)){
      //pthread_mutex_lock(&mutex);  
      counter++;
      AddToStack(buffer);
      fscanf(ifile, "%s", buffer);
      //pthread_mutex_unlock(&mutex);
    }
    fclose(ifile);
    printf("Thread #%ld added %d entries to the stack!n", tid, counter);
    //pthread_mutex_unlock(&mutex);
    //pthread_exit(NULL);
  }
  pthread_mutex_unlock(&mutex);
  pthread_exit(NULL);
  return NULL;
}
int main(int argc, char *argv[])
{
  pthread_t threads[NUM_THREADS];
  int rc, i = 0;
  long t;
  char **stack;
  FILE *ofile;
  for(t=0;t<NUM_THREADS;t++){
    printf("In main: creating thread %ldn", t);
    rc = pthread_create(&threads[t], NULL, FRead, (void *)t);
    if (rc){
      printf("ERROR; return code from pthread_create() is %dn", rc);
      exit(-1);
    }
  }

  for(t=0;t<NUM_THREADS;t++)
  {
    //pthread_join(threads[t],NULL);
  }

  //Lets write the content of the stack into a file
  stack = AddToStack(NULL); //Get the base of the stack pointer
  if (stack != NULL){
    ofile = fopen("result.dat", "w");
    for (i = 0; stack[i] != NULL; i++)
      fprintf(ofile, "%sn", stack[i]);
    fclose(ofile);
  }
  fprintf(stderr, "%d data written to file result.datn", i);
  pthread_exit(NULL);
  return 0;
}