Advanced Operating Systems   COMP9242 2002/S2

UNSW

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Thread Manipulation: lthread_ex_regs System Call Task has a fixed number (128) of threads, initially all but one inactive. Thread is activated by supplying a valid IP and SP. Thread inherits pager, excepter from activating thread. lthread_ex_regs() sets new and returns previous values for instruction pointer (IP), stack pointer (SP), exception handler, pager. Supplying invalid value (-1) to any of those retains original setting. Can be used for: performing a user-level thread switch (exchanging registers of running thread with saved ones); saving thread's context (by supplying only invalid parameters). Call terminates any pending or ongoing IPC. Note: A thread cannot be ``deleted'', it is stopped by blocking.