Interview Q&A / Operating Systems
Operating Systems interview questions
Processes, threads, scheduling, memory and deadlocks, in plain words.
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- What is a spinlock, and when is it better than a lock that puts the thread to sleep?
A spinlock makes a waiting thread loop on the CPU until the lock is free. It is better when the lock is held for a very short time, because sleeping and waking cost more than a brief spin.
IntermediateQuick answer1 min read - What is the Test-and-Set instruction and how does it provide mutual exclusion?
Test-and-Set is a hardware instruction that atomically reads a memory flag and sets it to 1. If it returned 0, the caller got the lock; if 1, someone else holds it. Because it is one indivisible step, two threads cannot both see 0.
AdvancedQuick answer1 min read