Until threads that are suspended or blocked become ready to run, the scheduler does not allocate any processor time to them, regardless of their priority (2/8)
Because Windows implements a preemptive scheduler, if another thread with higher priority becomes ready to run, the currently running thread might be preempted before finishing its time slice. (3/8)
When a running thread needs to wait, it give up the remainder of its time slice – The CONTEXT SWITCHES
A thread's context and the procedure for context switching vary depending on the processor's architecture. (4/8)
A thread's context and the procedure for context switching vary depending on the processor's architecture. (4/8)
A typical context switch requires saving and reloading the following data:
1. Instruction pointer
2. Kernel stack pointer
3. A pointer to the address space in which the thread runs (the process' page table directory) (5/8)
1. Instruction pointer
2. Kernel stack pointer
3. A pointer to the address space in which the thread runs (the process' page table directory) (5/8)
The kernel saves this information from the old thread by pushing it into the current (old thread's) kernel-mode stack, updating the stack pointer, and saving the stack pointer in the old thread's KTHREAD block. (6/8)
The kernel stack pointer is then set to the new thread's kernel stack, and the new thread's context is loaded. (7/8)
If the new thread is in a different process, it loads the address of its page table directory into a special processor register so that its address space is available. (8/8)
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