Operating Systems - Context Switch - Cost & Causes
When a timer interrupt triggers a context switch, what is the correct sequence of events that occur internally before the next process runs?
When a timer interrupt triggers a context switch, what is the correct sequence of events that occur internally before the next process runs?
easy🧠🧾 Concept Trace Q12 of Q15
Step-by-Step Solution
Step 1: Save current process state
Before switching, CPU registers of the current process must be saved to its PCB.Step 2: Scheduler decision
After saving, the scheduler selects the next process to run.Step 3: Load next process state
The CPU registers of the selected process are loaded from its PCB.Step 4: Resume execution
The CPU resumes execution with the new process context.Final Answer:
Option C -> Option CQuick Check:
Saving registers before scheduler decision and loading registers after is the correct order.
Quick Trick: Save first, then schedule, then load -> context switch order [OK]
Common Mistakes:
MISTAKES- Selecting next process before saving current registers
- Loading next process registers before scheduler decision
- Mixing order of save/load and scheduling
Trap Explanation:
PITFALL- Scheduler cannot select next process before current state is saved; loading registers before scheduling is illogical.
Interviewer Note:
CONTEXT- Tests understanding of the internal sequence during context switching.
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