/*  頭文件 */  
#include <stdio.h>  
#include <stdlib.h>  
#include <sys/types.h>  
#include <pthread.h>  
#include <signal.h>  
  
pthread_mutex_t mutex_one,mutex_two;  
pthread_mutex_t mutex;  
pthread_cond_t cond;  
  
void *thread_routine_one(void *arg)  
{  
    pthread_cond_wait(
 
&cond,&mutex);//確保two線程先運行  
  
    printf("thread_routine_one: lock mutex_one!\n");  
    pthread_mutex_lock(&mutex_one);  
  
    printf("thread_routine_one: lock mutex_two!\n");  
    pthread_mutex_lock(&mutex_two);//獲取two鎖，這個要等待two線程對two鎖的釋放  
  
    sleep(1);  
    printf("thread_routine_one: unlock mutex_two!\n
 
");  
    pthread_mutex_unlock(&mutex_two);  
  
    printf("thread_routine_one: unlock mutex_one!\n");  
    pthread_mutex_unlock(&mutex_one);  
  
    return NULL;  
}  
  
void *thread_routine_two(void *arg)  
{  
    printf("thread_routine_two: lock mutex_two!\n");  
    pthread_mutex_lock(
 
&mutex_two);//獲取two鎖  
    pthread_cond_signal(&cond);//讓one線程運行  
    sleep(1);//休眠，讓one可以先運行獲取one鎖  
  
    printf("thread_routine_two: lock mutex_one!\n");  
  
    pthread_mutex_lock(&mutex_one);//獲取one鎖，這個同樣必須等待one線程多one鎖的釋放  
  
    /**這時出現死鎖現象了，在two線程要等待one線程對one鎖的釋放，同時two鎖沒有釋放 
     * 然而在one線程需要等待two線程對two鎖的釋放，然後才會對one鎖的釋放！出現相互等待的過程**/  
  
    printf("thread_routine_two: unlock mutex_one!\n");  
    pthread_mutex_unlock(&mutex_one);  
  
    printf("thread_routine_two: unlock mutex_two!\n");  
    pthread_mutex_unlock(&mutex_two);  
  
    return NULL;  
}  
  
void main()  
{  
    pthread_t pthread_one,pthread_two;  
  
    pthread_mutex_init(&mutex_one,NULL);  
    pthread_mutex_init(&mutex_two,NULL);  
    pthread_mutex_init(&mutex,NULL);  
    pthread_cond_init(&cond,NULL);  
  
    pthread_create(&pthread_one,NULL,thread_routine_one,NULL);  
    pthread_create(&pthread_two,NULL,thread_routine_two,NULL);  
  
    while(1)  
        sleep(1);  
}  

線程程A已經擁有至少一個資源，此時又去申請其他資源，而該資源又正在被B線程使用，而同時B線程也在等待A線程的資源釋放後才會釋放自己的資源，便會造成死鎖。此時請求進程阻塞，但對自己已經獲得的資源保持不放，

線程死鎖例子