Unformatted text preview: used. 2. (a) Low priority task L runs, obtains lock R. Medium priority task M then preempts L and obtains lock S, then later blocks when it requests lock R held by task L, so L resumes execution (direct blocking). Then task H preempts task L and blocks when it requests lock S held by task M. Task M is still blocked waiting for lock R, so task L again resumes. Task H blocks on S held by M, which blocks on R held by L (pass-through blocking). (b) Low priority task L runs, obtains lock R. Medium priority task M then preempts L and runs until it is preempted by high priority task H. H runs until it requests R, at which point it blocks waiting for L to release R. However, M is higher priority, so M runs instead of L, in effect giving it higher priority than H as long as H is blocked waiting for L....
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- Fall '08
- Operating Systems, Blocking, Amdahl's law, Priority inversion, Amdahl, maximum speedup