AtomicBoolean: add compare_and_set API

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难度
3/5
预计耗时
1-2 天
新手友好度
35/100
Issue 类型
功能
描述清晰度
基本清楚
活跃度
停滞
技术栈
ruby
领域
backend

调研方向

Start by locating the AtomicBoolean implementation and its current value API. Review how the existing atomic value behavior is tested, then determine where the compare_and_set entry point belongs. Done means the proposed API supports the false-to-true use case described in the issue and its behavior is covered by the project’s tests.

由索引模型根据 Issue 内容生成。

描述

enhancement looking-for-contributor medium-priority

Compare-and-set is a useful functionality (that's why it exists in the Java API). It can save one from race conditions, as explained below.

Use case
  • Assume an atomicboolean called LOCKED, set to false.
  • Multiple concurrent threads run the following code:
if !LOCKED.value
  LOCKED.value = true
  # do something ....
  LOCKED.value = false
end

In this scenario, concurrent threads can read a false in if !LOCKED.value, and enter the if block. That defeats the purpose of an atomicboolean-backed lock.

If there was a CAS API, the fixed code would look like this:

if LOCKED.compare_and_set(false, true)

Furthermore

Ruby has no "tryLock" either. So it's not immediately obvious how to create non-blocking synchronized code. Boolean CAS would offer a nice alternative which Java programmers (and others) already are familiar with.

What do you think?

Cheers - Victor

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