Assignment6

Exercise Sheet 6

In this exercise sheet you will use POSIX threads and test out different methods for mutual exclusion and synchronization.

Task 1

Write a program which spawns 10 threads.

• Each thread waits for a random time between 0 and 3 seconds, then creates a file called threadN.txt (where N is the thread number between 0 and 9) and writes its thread id (returned by gettid) to this file. Ensure that the file is closed in case a thread opens it and is subsequently interrupted (study the pthread_cleanup family of functions).
• After spawning all threads, the main program decides for each thread whether to randomly cancel it, with a chance of cancellation of 50%.
• Afterwards, the main program waits for all threads to exit.

Task 2

In this exercise you will implement a single producer multiple consumer pattern.

Your program should spawn 5 threads, the consumers, which all try to read elements from a queue. Queued elements are of type unsigned.

Note: You can use e.g. the C++ std::queue (a short example demonstrating its usage is provided in producer_consumer.cpp) or the basic C queue that is provided in myqueue.h (a short example demonstrating its usage is provided in producer_consumer.c).

• When a consumer thread successfully reads an element, it adds it to its local sum. When the element is 0, it prints out the sum and exits.

• The main thread acts as the producer. After spawning all 5 consumers, it feeds 10.000 1 entries into the queue, followed by 5 0 entries.

Access to the queue should be protected by using the pthread_mutex facilities.