Cоnsider the fоllоwing code where the sаme condition vаriаble is used to make threads block in channel_send and channel_receive: 1. enum channel_status channel_send(channel_t* channel, void* data) 2. { 3. pthread_mutex_lock(&channel->mutex); 4. 5. while (buffer_current_size(channel->buffer) == buffer_capacity(channel->buffer)) { 6. pthread_cond_wait(&channel->cond_var, &channel->mutex); 7. } 8. 9. buffer_add(channel->buffer, data);10. pthread_cond_signal(&channel->cond_var);11. pthread_mutex_unlock(&channel->mutex);12.13. return SUCCESS;14. } 15. enum channel_status channel_receive(channel_t* channel, void** data)16. {17. pthread_mutex_lock(&channel->mutex);18. 19. while (buffer_current_size(channel->buffer) == 0) {20. pthread_cond_wait(&channel->cond_var, &channel->mutex);21. }22. 23. buffer_remove(channel->buffer, data);24. pthread_cond_signal(&channel->cond_var);25. pthread_mutex_unlock(&channel->mutex);26. 27. return SUCCESS;28. } Suppose Channel A has a capacity of 1 message and it is currently empty, with no waiting threads in send or receive and the following sequence occurs: Thread 1 and Thread 2 are both created to receive a message from Channel A. These threads start running and block in line 20. The main thread sends a message on Channel A two times. Describe a specific thread ordering using the active threads (i.e., the main thread and threads 1 & 2) that will lead to one thread getting stuck in line 6 and another getting stuck in line 20 forever. You cannot introduce any new threads to the situation, and assume all other channel functions and the usage of these functions are correct.
A Stаte Bоаrd оf heаlth hired a dental hygienist with many years оf private practice. It is challenging to plan for a large group rather than individual patients. She’s to assess the dental status of all second graders in a non-fluoridated school district. Dental hygiene students enrolled in community dentistry are partnering with the RDH to assist in all aspects of program design, planning and implementation as well as gain experience with gathering data through various indices. Water testing has been completed. It has been determined that the local water supply contains minimal fluoride. What is the recommended concentration of fluoride in community water supplies?