Why it matters

Wrong synchronization causes races, deadlocks, or serialized bottlenecks. Understanding primitives makes concurrent code correct and performant.

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The architecture

Lock (mutex): exclusive access. One thread at a time inside critical section.

Semaphore: N-thread access. Bounded concurrency.

Condition variable: wait for a condition; signaled by another thread.

Synchronization primitivesLockexclusiveSemaphoreN-threadCondition varwait/signalBarrier: N threads must all reach a point before any continues; used in parallel algorithms
Common primitives.
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How it works end to end

Read-write lock: multiple readers, one writer. Better for read-heavy.

Barrier: wait until N threads reach point, then all proceed.

Reentrant lock: same thread can acquire multiple times; unlock N times to release.