CODEWITHSUNDEEP
c++cpthreadspthread-join
Yogesh lele
Yogesh lele

Reputation: 412

How to join threads created dynamically in c/c++

I have written a C/C++ code which implements socket connection and the main thread is in continuous loop listening at its port. When a connection request comes at this port, I have spawned a thread using pthread calls and offloaded the work on this thread. As such i have 'n' threads getting created dynamically for 'n' incoming requests. The problem is that, if one thread terminates the main thread also terminates.

I have used pthread_join() but It waits for the thread in the argument to finish.In my case, the new threads are not getting spawned once the call to pthread_join() is made.

pthread_t t;
while(1)    //server always to be in listen mode
 {
  client_len=sizeof(client_sockaddr);
  client_sockfd=accept(server_sockfd,(struct sockaddr*)&client_sockaddr,&client_len);


  pthread_create(&t,NULL,server_thread,(void*)client_sockfd);

  (void)pthread_join(t,NULL);

  }

Upvotes: 3

Views: 1528

Answers (2)

sujin
sujin

Reputation: 2853

Add printf("check string\n"); after pthread_join in your code. compile and run it now. You might get some idea about your problem.

You will not meet printf function.

Reason for the behavior is pthread_join will wait for first created thread to finish the job.

so unless and until first thread finish the job new thread will not created. So your code will not accept any new client connection.

So don't use pthred_join inside your while(1) then your problem will be solved.

pthread_join is mostly useful when main process want to wait until thread finishes the job.

Upvotes: 0

Casey
Casey

Reputation: 42554

If you don't care about the return value from your threads, and you're not interested in when they complete, then you should detach them with pthread_detach or simply create them in a detached state to begin with:

pthread_attr_t thread_attr;
pthread_attr_init(&thread_attr);
pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
while(1)    //server always to be in listen mode
{
  client_len=sizeof(client_sockaddr);
  client_sockfd=accept(server_sockfd,(struct sockaddr*)&client_sockaddr,&client_len);

  pthread_t t;
  pthread_create(&t,&thread_attr,server_thread,(void*)client_sockfd);
}
pthread_attr_destroy(&thread_attr);

Upvotes: 3

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