1. What three conditions must be satisfied in order to solve the critical section problem?
: In a solution to the critical section problem, no thread may be executing in its critical section if a thread is currently executing in its critical section. Furthermore, only those threads that are not executing in their critical sections can participate in the decision on which process will enter its critical section next. Finally, a bound must exist on the number of times that other threads are allowed to enter their critical state after a thread has made a request to enter its critical state
2. Explain what has to happen for a set of processes to achieve a deadlocked state.
: For a set of processes to exist in a deadlocked state, every process in the set must be waiting for an event that can be caused only be another process in the set. Thus, the processes cannot ever exit this state without manual intervention
3. Explain the basic method for implementing paging.
: Physical memory is broken up into fixed-sized blocks called frames while logical memory is broken up into equal-sized blocks called pages. Whenever the CPU generates a logical address, the page number and offset into that page is used, in conjunction with a page table, to map the request to a location in physical memory
4. Explain the sequence of events that happens when a page-fault occurs.
: When the operating system cannot load the desired page into memory, a page-fault occurs. First, the memory reference checks for validity. In the case of an invalid request, the program will be terminated. If the request was valid, a free frame is located. A disk operation is then scheduled to read the page into the frame just found, update the page table, restart the instruction that was interrupted because of the page fault, and use the page accordingly
5. Describe three common methods for remote file-sharing.
: The first implemented method involves manually transferring files between machines via programs like ftp. The second major method uses a distributed file system (DFS), in which remote directories are visible from a local machine. In the third method, a browser is needed to access remote files on the World Wide Web, and separate operations (essentially a wrapper for ftp) are used to transfer files. The DFS method involves a much tighter integration between the machine that is accessing the remote files and the machine providing the files
Assignment solution 2
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