# Barrier (OpenMP)
**Barrier** is a synchronisation point where all threads in a team wait until every member has arrived.

OpenMP inserts an implicit barrier at the end of every `parallel`, `for`, and `sections` region. All threads wait there until every member of the team has arrived. An explicit `#pragma omp barrier` adds a synchronisation point mid-region, which is needed when one group of threads produces data that another group will consume in the same parallel block.

```c
#pragma omp parallel
{
    fill(omp_get_thread_num());   // each thread fills its slice
    #pragma omp barrier           // wait for all threads to finish filling
    read(omp_get_thread_num());   // now safe to read any slice
}
```