如何防止死锁？

Question

I've been struggling with a synchronization problem for a while. I've got a process A, this is the main one, and 3 processes of type B. These processes have to signal A and wait for response.

A is waiting for all 3 signals. When they all arrive, A does it's job and signals all B processes back so they can continue their work.

A:
   if(/*all signals received*/)  {
     //do my job
     //signal all Bs
   }

B:
   //some code
   signal(A);
   pause();  //wait for response
   //Do other stuff

When B calls signal(A) , A does his job, signals B back, then schedules B again causing B to call pause() and wait for a signal indefinitely. I don't know how to prevent this deadlock.

Is there any other way to achieve this?

Answer 1

Consider using semaphore as IPC synchronization,
any process want to send signal have to lock the semaphore,
and after receiveing A's return, unlocking it so next process can proceed.