Operating System

lock critical sections atomic

coarse-grained fine-grained

how to build a efficient lock

evaluating locks

criteria fairness performance

Solution 1: controlling interrupts

benefits: simplicity negatives: privileged :dangerous not working on multiprocessor machine interrupts may lost inefficient

failed attempt: Loads/Stores

test-and-set I think it’s just fetch and set although the name test is given for you can test the old value with return value. compare-and-swap load-linked and store-conditional

too much spinning

yielding cpu running, ready, blocking self deschedule still loop running and yielding starvation: some thread still may not be able to execute

sleeping instead of yielding pack,unpack spin lock with queue determine which thread to run next, pack to sleep until some call unpack(threadid) wakeup/waiting race: setpark

futex