# Problem with condition with @async threads?

**URL:** <https://discourse.julialang.org/t/problem-with-condition-with-async-threads/95147>\
**Category:** General Usage\
**Tags:** question\
**Created:** [February 24, 2023, 4:14pm UTC](https://discourse.julialang.org/t/problem-with-condition-with-async-threads/95147 "2023-02-24T16:14:16Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Amro](https://avatars.discourse-cdn.com/v4/letter/a/4491bb/32.png) [@Amro](https://discourse.julialang.org/u/Amro)\
**Post date:** [February 24, 2023, 4:14pm UTC](https://discourse.julialang.org/t/problem-with-condition-with-async-threads/95147/1 "2023-02-24T16:14:16Z")

</div>

I want to synchronize between threads by using `notify&wait` as in the example MWE, in which `nthreads()=3`. Each thread executes `for-loop` and `while-loop` inside it. It is similar to what mentioned in [Can the threads synchronized by channel?](https://discourse.julialang.org/t/can-the-threads-generated-by-tspawnat-synchronized-by-channel/95043/14), but with different way of synchronization primitives.

In the MWE, I want to let the threads execute in order:  
1- All enter the while-loop together. By using `condition_main` so thread-1 synchronize with `2&3`.  
2- At each iteration of the while-loop, thread-1 sets `status = true` and notify other threads to inter the while-loop. In each iteration of the `while-loop`, the first thread executes `Block-1` and notify other threads to print their statements via `condition_main`, and wait until they finish by using `condition_threads` to move to the following iteration of the while-loop.  
3- When `status = false`, all threads move to the following iteration of the for-loop.  
Please note, I dont need to use `sleep` function to avoid killing the performance.

```julia
function NN()
  condition_main = Condition()
  condition_threads = [Condition() for _ in 1:nthreads()-1]
  status = true
  @threads for _ in 1:nthreads()
      if threadid() == 1
        @async begin
          for t in 1:2
            iter = 0
            status = true
            notify(condition_main)
              while status
                # Start Block-1
                println("Iteration $t Thread $(threadid()) Update status")
                iter += 1
                if iter == 2
                  status = false
                end
                # Block-1
                notify(condition_main)
                wait.(condition_threads)
              end # while status
          end # for t in 1:2
        end # @async begin
      else # if threadid() == 1
        @async begin
          for tt in 1:2
            wait(condition_main)
                while status
                  wait(condition_main)
                  println("Iteration $tt Thread $(threadid()) Execution")
                  notify(condition_threads[threadid()-1])
                end #while status
          end # for t in 1:2
        end #@async begin
      end # if threadid() == 1
  end # @threads for _ in 1:nthreads()
  return nothing
end
NN()

```

I expect the results to show as below:

```julia
Iteration 1 Thread 1 Update status
Iteration 1 Thread 2 Execution
Iteration 1 Thread 3 Execution
Iteration 1 Thread 1 Update status
Iteration 1 Thread 2 Execution
Iteration 1 Thread 3 Execution

Iteration 2 Thread 1 Update status
Iteration 2 Thread 2 Execution
Iteration 2 Thread 3 Execution
Iteration 2 Thread 1 Update status
Iteration 2 Thread 2 Execution
Iteration 2 Thread 3 Execution

```

However, I am having only as below because it is freezes. Any help please?

```julia
Iteration 1 Thread 1 Update status

```