銀行家的算法與pthreads

Question

我想在c編寫一個銀行家的算法問題，但我得到分段錯誤。我已經多次運行我的代碼，但我似乎無法找出故障發生的位置。我對互斥體和pthread庫相當陌生。任何幫助，將不勝感激。由於

//Bankers Algorithm 
#include <stdio.h> 
#include <pthread.h> 
#include <stdlib.h> 
#include <unistd.h> 

#define MAXN 10    /* maximum number of processes     */ 
#define MAXM 10    /* maximum number of resource types    */ 
int ProcCurr[3][3];  /* 3 threads(processes), 3 resources */ 
int temp[3][3];  /* temp array location   */ 
int Available[10];  /* Available[m] = # resources unallocated */ 
int Max[3][3] = { {10,10,10},{10,10,10},{10,10,10} }; /* Max[n][m] = max demand of processes n for resource m */ 
int Allocation[3][3] = { {1,2,3},{3,2,1},{1,1,1} }; /* Allocation[n][m] = # resources m allocated to processes n*/ 
int Need[3][3];  /* Need[n][m] = resources m needed by processes n   */ 
int counti = 0;    /* Need[n][m] = Max[n][m] - Allocation[n][m]  */ 
int countj = 0; 
int threadsi = 3; 
int threadsj = 3; 

void *inc_count(void *r); 
void *watch_count(void *r); 

pthread_mutex_t mutex; /*mutex id*/ 
pthread_cond_t count_threshold_cv; 

int main() 
{ 
    pthread_t ProcCurr[3][3]; /*id of thread*/ 
    pthread_attr_t attr; 
    int i, j; 
    long r1 = 1,r2 = 2,r3 = 3; 

    if(pthread_mutex_init(&mutex, NULL) < 0){ 
    perror("Pthread_mutex_init error."); 
    exit(1);  
    } 
    else 
    //pthread_mutex_init(&mutex, NULL); 

    pthread_cond_init(&count_threshold_cv, NULL); 

    pthread_attr_init(&attr); /*get default attributes*/ 

    pthread_create(&ProcCurr[0][0], &attr, watch_count, (void *)r1); 
    pthread_create(&ProcCurr[1][0], &attr, inc_count, (void *)r2); 
    pthread_create(&ProcCurr[2][0], &attr, inc_count, (void *)r3); 


    for(i=0; i<=threadsi; i++){ 
     for(j=0; j<=threadsj; j++){ 
      //pthread_join(ProcCurr[i][j],NULL); /*wait for thread to exit*/ 
      pthread_join(ProcCurr[0][0],NULL); 
      pthread_join(ProcCurr[1][0],NULL);    
      pthread_join(ProcCurr[2][0],NULL); 
      } 
     } 
    printf("Main: waited on %d, %d threads. Done.\n", threadsi, threadsj); 

    pthread_attr_destroy(&attr); 
    pthread_mutex_destroy(&mutex); 
    pthread_cond_destroy(&count_threshold_cv); 
    pthread_exit(NULL); 

} 

void *inc_count(void *r) 
{ /*processes are running, thread of process is initalize to something <=3, each threads request up to 3 resources, when all resources are commited then next thread will have to wait (mutex goes to resource from a thread letting other threads know not to this resource)*/ 
    int i, j, n, m; 
    long my_id = (long)r; 

    for(i=0; i<10; i++){ 
     for(j=0; j<10; j++){ 
    Need[n][m] = Max[n][m] - Allocation[i][j]; 
    printf("Allocation = %d, Need = %d\n", Allocation[i][j], Need[n][m]); 
    } 
    pthread_mutex_lock(&mutex); 
    if(counti == MAXN && countj == MAXM){ 
     pthread_cond_signal(&count_threshold_cv); 
     printf("inc_count: thread %ld, Need = %d. Threshold reached.\n",my_id, Need[n][m]); 
     } 
    printf("inc_count: thread %ld, Need = %d. Unlocking mutex.\n", my_id, Need[n][m]); 
    pthread_mutex_unlock(&mutex); 
    sleep(1); 
    watch_count(r); 
    } 
    pthread_exit(NULL); 
    watch_count(r); 

} 

void *watch_count(void *r) 
{ 
    long my_id = (long)r; 
    int n, m; 

    printf("Start watch_count: thread %ld\n", my_id); 

    while(counti < MAXN && countj <MAXM) 
    { pthread_mutex_lock(&mutex); 
    Available[n] = Max[n][m] - Allocation[counti++][countj++]; 
    printf("Available = %d\n", Available[n]); 
    pthread_cond_wait(&count_threshold_cv, &mutex); 
    printf("watch_count: thread %ld, available = %d. Conditional Signal Received.\n", my_id, Available[m]); 
    countj++; 
    printf("watch_count: thread %ld, Need now = %d.\n", my_id, Need[counti][countj]); 
    } 
    pthread_mutex_unlock(&mutex); 
    pthread_exit(NULL); 
} 

Answer 1

結束以及在inc_count：

你沒有初始化n和m，但你在使用它：

Need[n][m] = Max[n][m] - Allocation[i][j]; 

但是你聲明：

int Need[3][3] 

如果n和/或m是> = 3？ Segfault！

而且，你有嵌套循環for使用索引i和j是從0到10，那麼你正在使用Allocation[i][j]但你有靜態與尺寸3x3的分配是：

int Allocation[3][3] = { {1,2,3},{3,2,1},{1,1,1} }; 

Answer 2

int threadsi = 3; 
int threadsj = 3; 
: 
pthread_create(&ProcCurr[0][0], &attr, watch_count, (void *)r1); 
pthread_create(&ProcCurr[1][0], &attr, inc_count, (void *)r2); 
pthread_create(&ProcCurr[2][0], &attr, inc_count, (void *)r3); 
: 
for(i=0; i<=threadsi; i++){ 
    for(j=0; j<=threadsj; j++){ 
     pthread_join(ProcCurr[i][j],NULL); 
    } 
} 

你似乎開始三個線程，然後對他們的加盟，其中6將具有零填充線程ID值。

這是不可能:-)