All MCQs

A signal makes an eligible waiter runnable so it can recheck the condition while holding the lock.
Because the condition may change again, awakened threads normally test it in a loop.

Condition-variable wait atomically releases the monitor lock and blocks the caller.
After awakening, the thread reacquires the lock before continuing.

A monitor groups shared state with operations that execute under implicit mutual exclusion.
This reduces the chance of forgetting to acquire and release an external lock correctly.

The signal operation returns a resource unit or announces that an event has occurred.
A blocked waiter may become eligible to run after the count is increased.

The wait operation acquires one represented resource when the semaphore count permits it.
If none is available, the caller waits according to the semaphore implementation.

A counting semaphore maintains a nonnegative count corresponding to available resource instances.
Each acquisition decrements the count, and each release increments it.

A binary semaphore uses two logical states and can provide mutual exclusion or event signaling.
A counting semaphore represents multiple available units of a resource.

A mutex has ownership semantics and protects a critical section from concurrent conflicting access.
A thread acquires it before entering and releases it after leaving.

Lock-free progress means some operation completes in a finite number of system-wide steps despite contention.
It is weaker than wait-free progress, which guarantees completion for every individual thread.

Atomic variables provide operations that other threads cannot observe halfway through.
They may store several data types and often support operations such as load, store, exchange, and compare-and-swap.

Modern processors and compilers may reorder memory operations unless constrained.
A memory barrier ensures required reads and writes become visible in the intended order.

Busy waiting repeatedly executes instructions while waiting for a state change.
Unlike blocking, it does not release the processor for other work during the wait.