我寫了一個簡單的多線程C程序來訪問MySQL,它工作正常,除了,當我在每個線程函數中添加usleep()或sleep()函數。 我創建在主方法二並行線程,多線程訪問MySQL錯誤
int main(){
mysql_library_init(0,NULL,NULL);
printf("Hello world!\n");
init_pool(&p,100);
pthread_t producer;
pthread_t consumer_1;
pthread_t consumer_2;
pthread_create(&producer,NULL,produce_fun,NULL);
pthread_create(&consumer_1,NULL,consume_fun,NULL);
pthread_create(&consumer_2,NULL,consume_fun,NULL);
mysql_library_end();
}
void * produce_fun(void *arg){
pthread_detach(pthread_self());
//procedure
while(1){
usleep(500000);
printf("producer...\n");
produce(&p,cnt++);
}
pthread_exit(NULL);
}
void * consume_fun(void *arg){
pthread_detach(pthread_self());
MYSQL db;
MYSQL *ptr_db=mysql_init(&db);
mysql_real_connect();
//procedure
while(1){
usleep(1000000);
printf("consumer...");
int item=consume(&p);
addRecord_d(ptr_db,"test",item);
}
mysql_thread_end();
pthread_exit(NULL);
}
void addRecord_d(MYSQL *ptr_db,const char *t_name,int item){
char query_buffer[100];
sprintf(query_buffer,"insert into %s values(0,%d)",t_name,item);
//pthread_mutex_lock(&db_t_lock);
int ret=mysql_query(ptr_db,query_buffer);
if(ret){
fprintf(stderr,"%s%s\n","cannot add record to ",t_name);
return;
}
unsigned long long update_id=mysql_insert_id(ptr_db);
// pthread_mutex_unlock(&db_t_lock);
printf("add record (%llu,%d) ok.",update_id,item);
}
像節目輸出錯誤:
[Thread debugging using libthread_db enabled]
[New Thread 0xb7ae3b70 (LWP 7712)]
Hello world!
[New Thread 0xb72d6b70 (LWP 7713)]
[New Thread 0xb6ad5b70 (LWP 7714)]
[New Thread 0xb62d4b70 (LWP 7715)]
[Thread 0xb7ae3b70 (LWP 7712) exited]
producer...
producer...
consumer...consumer...add record (31441,0) ok.add record (31442,1) ok.producer...
producer...
consumer...consumer...add record (31443,2) ok.add record (31444,3) ok.producer...
producer...
consumer...consumer...add record (31445,4) ok.add record (31446,5) ok.producer...
producer...
consumer...consumer...add record (31447,6) ok.add record (31448,7) ok.producer...
Error in my_thread_global_end(): 2 threads didn't exit
[Thread 0xb72d6b70 (LWP 7713) exited]
[Thread 0xb6ad5b70 (LWP 7714) exited]
[Thread 0xb62d4b70 (LWP 7715) exited]
Program exited normally.
,當我在功能addRecord_d的pthread_mutex_lock添加,錯誤依然存在。 那究竟是什麼問題呢?
嗨邁克,謝謝你的幫助。 當我用上面提供的代碼替換相應的代碼時,會創建四個線程並很快出現,輸出結果就是「hello world」。 所以我覺得可能會有一些錯誤的主要方法,真的,我忘了補充join方法,所以我跑終止的主要方法,而其他三個線程仍然活着的風險。 將pthread_join()添加到主方法的末尾,錯誤不再發生。 嗯,我是多線程編程的新手,你的回覆讓我想起了加入方法,謝謝。 – user188916 2009-12-17 03:16:02
以及即時通訊嘗試在我的另一個測試源上使用你的建議,但一旦它運行mysql說「太多連接」,你有更好的主意嗎? – capede 2011-06-18 18:19:46