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How could we implement locks? No matter how we choose to implement them, we must have some hardware support. One possibility for implementing locks on a uniprocessor machine is is to disable interrupts when testing/setting locks. With interrupts disabled on a single processor machine, the processor cannot switch processes, and so we can guarantee that only the active process will have access to the shared data. Another option would be to make use of atomic operations, such as test and set. This type of operation (which usually corresponds to a single atomic assembly instruction) behaves as if it used the following C function, atomically:
int test_and_set(int x) // let x be strictly either 0 or 1.{if (x) { return 1; } else { x=1; return 0; }}
All this needs to be implemented atomically, in hardware. Using this type of atomic operation, one could implement thread lock(l) simply as while test_and_set(l) {
; // do nothing} // spinlock version of thread_lock()and thread unlock(l) simply asl = 0; // we need this to be an atomic clear (or assign) instruction
The assembly instruction test and set can bemade to be atomic acrossmultiple processors. An equivalent option would be an atomic compare and swap assembly instruction. These low-level hardware solutions are then built up into high-level functions, either built into the languages, or in libraries. In general, do not implement your own locking functions, but rather use functions from a tested library. Getting things right can be tricky, and your own solution is also likely to be non-portable.
Write a short note on disk scheduling One of the responsibities of operating system O/S is to use the hardware efficiently. Whenever a process requires I/O to or from the
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What are turnaround time and response time? Turnaround time is the interval among the submission of a job and its completion. Response time is the interval among submission
What is a semaphore? A semaphore 'S' is a synchronization tool which is an integer value that, apart from initialization, is accessed only by two standard atomic operations; w
Deadlocks can be detected while the program is running, by running cycle detection algorithms on the graph that de?nes the current use of resources. De?ne this graph as follows:
To evade race condition, the maximum number of processes that may be at the same time inside the critical section is The maximum number of processes which may be at the same t
What is an acyclic graph? A tree that has been corrupted by links to other branches, but does not have any cyclic paths in it.
properies of Batch oriented and interactive operating system.
my Operating System is windows trust but when the windows start say its windows xp. help pleaes
Explain process scheduling in time sharing The relevant features of time sharing are: 1. Process priorities do not depend on the nature of the processes 2. Proc
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