Operating Systems - System Call - Mechanism & Modes (User vs Kernel)
If you extend the OS to allow user-level threads to make system calls without blocking the entire process, which modification is essential to the system call mechanism?
If you extend the OS to allow user-level threads to make system calls without blocking the entire process, which modification is essential to the system call mechanism?
hard🎤 Interviewer Follow-up Q10 of Q15
Step-by-Step Solution
Solution:
Step 1: Understand user-level threads and system calls
User-level threads require independent kernel context to avoid blocking others.Step 2: Identify necessary kernel support
Per-thread kernel stacks and context enable independent mode switches and system call handling.Step 3: Evaluate other options
Disabling mode switch or sharing kernel stack causes blocking or corruption; async signals don't replace system calls.Final Answer:
Option A -> Option AQuick Check:
Per-thread kernel context enables non-blocking system calls. [OK]
Quick Trick: Per-thread kernel stacks enable independent system calls [OK]
Common Mistakes:
MISTAKES- Thinking mode switch can be disabled
- Assuming shared kernel stack is safe
- Believing async signals replace system calls
Trap Explanation:
PITFALL- Candidates often overlook kernel support needed for user-level threading and system calls.
Interviewer Note:
CONTEXT- Probes deep understanding of threading and system call interaction.
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