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CS533 Concepts of Operating Systems Class 7

CS533 Concepts of Operating Systems Class 7. Integrated Task and Stack Management. Questions. What do these terms mean? process, thread, kernel-level thread, user-level thread, fiber? user-level thread stack, user stack, kernel stack? Address space?. Questions.

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CS533 Concepts of Operating Systems Class 7

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  1. CS533 Concepts of Operating SystemsClass 7 Integrated Task and Stack Management

  2. Questions • What do these terms mean? • process, thread, kernel-level thread, user-level thread, fiber? • user-level thread stack, user stack, kernel stack? • Address space? CS533 - Concepts of Operating Systems

  3. Questions • How might a user-level thread library support synchronous I/O calls for its threads without losing control of the CPU due to blocking? • How does this approach behave during page-faults? • Does this matter? • Can it deal with preemptions? • Do user-level thread libraries do “stack ripping”? CS533 - Concepts of Operating Systems

  4. Questions • In what way are user-level threads “faster” than kernel-level threads? • Aren’t we just layering abstractions on abstractions? • Why can’t you do preemptive user-level thread scheduling without special kernel support? • Does this mean you can only do sequential task management? • Can you do cooperative task management? • How? CS533 - Concepts of Operating Systems

  5. Questions • Is synchronization needed for cooperative user-level scheduling on uniprocessors? • What precautions must you take? • Is synchronization needed on multiprocessors? • How are synchronization operations such as spin-locks and semaphores implemented, i.e., how do you spin and how do you block? • For user level threads? • For kernel level threads? CS533 - Concepts of Operating Systems

  6. Questions • What stack management model do most OS kernels export? • How are I/O and page faults events handled? • What differences are there between virtual CPUs (threads) and real CPUs (hardware)? • How are I/O and page fault events handled? • How is time managed? • What similarities do kernel-provided scheduler activations have to hardware-provided interrupts? CS533 - Concepts of Operating Systems

  7. Questions • What synchronization-related issues do you have to worry about when writing an interrupt handler? • What about a scheduler activation handler? • Why must the user-level thread library be reentrant? • How is its pattern of entry points and synchronization concerns similar to OS kernel code? CS533 - Concepts of Operating Systems

  8. Questions • How might a scheduler activation handler deadlock? • What would a prevention-based solution look like? • What problems would it have? • What would a recovery-based solution look like? • What problems would it have? • Why does the kernel delay delivery of a second page-fault SA until the first page-fault SA on the same address has completed? CS533 - Concepts of Operating Systems

  9. Questions • What happens immediately following I/O completion if the calling thread still has more kernel code to execute? • In what ways do scheduler activations mix manual and automatic stack management models? • Are they a translation point / boundary between the two models? CS533 - Concepts of Operating Systems

  10. Reminder • Class 8 presenters • Discuss your presentation plans with me ahead of time • Mail me the final version of your slides BEFORE the class CS533 - Concepts of Operating Systems

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