Acquire semantics

As explained in C# Concurrency: Asynchronous and multithreaded programming

Acquire semantics are memory-ordering guarantees that prevent reads from being moved earlier than a synchronization operation.

Acquire semantics prevent reads from moving earlier than a synchronization operation. Lock acquisition provides this guarantee, helping a thread observe shared data after another thread releases its lock. section 7.2

Use acquire semantics together with the complementary ordering rules:

• Treat lock acquisition as an acquire operation and lock release as a release operation. section 7.2
• Prefer locks for shared data; relying on volatile does not guarantee the latest value and can introduce further problems. section 7.2
• Distinguish acquire and release semantics from memory barriers, which constrain reads and writes in both directions. section 7.2

Figure 7.1 Acquire and release semantics

Use the acquire-and-release diagram to visualize how synchronization limits compiler and CPU memory reordering. section 7.2

How C# Concurrency: Asynchronous and multithreaded programming covers it

How deep it goes

Defines read-order constraints, contrasts release and barrier semantics, and stops short of detailed CPU-level implementation.

Examples

Uses shared initialization, lock acquisition and release, volatile access, and a diagram of reordered memory operations.

What it assumes

Assumes shared-memory multithreading and teaches memory reordering through locks, reads, writes, and synchronization operations.

What you can do after

Apply lock-based synchronization when accessing data shared between threads.

How it connects

Connects acquire semantics with release semantics, memory barriers, the memory model, locks, volatile, and deadlocks.

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Also explained in

• 

  liveBookmanning.com
  C++ Concurrency in Action, Second EditionAn acquire operation is an atomic operation whose ordering can synchronize with a release operation on the same memory location.
• 

  liveBookmanning.com
  Modern CAn acquire operation is a concurrency operation that establishes visibility of effects published by a corresponding release.
• 

  liveBookmanning.com
  Modern C, Third EditionAcquire semantics are memory-ordering properties that make effects preceding a matching release operation visible after the acquire operation.
• 

  liveBookmanning.com
  LatencyAn acquire memory barrier prevents subsequent memory operations from being reordered before a synchronization operation and observes effects published by a releasing operation.

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Related concepts

• acquire-release semanticsconfigures · Acquire-release semantics are memory-ordering rules under which release operations make preceding effects visible to acquire operations that synchronize with them.
• memory barrieruses · A memory barrier is a synchronization operation that constrains the ordering or visibility of memory accesses across concurrent execution.

This explainer was generated by Manning's knowledge graph from the text of C# Concurrency: Asynchronous and multithreaded programming. The section links point to the parts of the book it draws on.