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All threads may not be equal readylist data when gets

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Unformatted text preview: l threads may not be equal readyList data when gets de-scheduled … Thread Thread Scheduling (cont’d) The scheduler makes a sequence of “moves” that determines the the interleaving of threads. • Programs use synchronization to prevent “bad moves”. • …but otherwise scheduling choices appear (to the program) to be nondeterministic. The scheduler’s moves are dictated by a scheduling policy Applies to process scheduling as well Thread Thread Scheduling (cont’d) Priority scheduling threads have a priority scheduler selects thread with highest priority to run preemptive or non-preemptive Priority inversion 3 threads, t1, t2, and t3 (priority order – low to high) t1 is holding a resource (lock) that t3 needs t3 is obviously blocked t2 keeps on running! BREAK BREAK CSci CSci 5103 Operating Systems User/Kernel Threads PopPop-Up Threads Create cheaper than restore; still have to save state of prior thread Idea: if you are already in the kernel a new message comes in, 31 create new thread Implementing Implementing Threads in User Space A user-level threads package 32 Implementing Implementing Threads in the Kernel A threads package managed by the kernel 33 Pros of kernel threads: Pros of user threads: Hybrid Implementations Hybrid Implementations – best of both … Multiplexing user-level threads onto kernel- level threads Solaris is one example 35 Really Really want to maintain user threads Comparing user-level threads, kernel thr...
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