compare-and-swap | 易学教程

Atomically increment two integers with CAS

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问题 Apparently, it is possible to atomically increment two integers with compare-and-swap instructions. This talk claims that such an algorithm exists but it does not detail what it looks like. How can this be done? (Note, that the obvious solution of incrementing the integers one after the other is not atomic. Also, stuffing multiple integers into one machine word does not count because it would restrict the possible range.) 回答1: Make me think of a sequence lock. Not very accurate (putting this

Java Concurrency: CAS vs Locking [closed]

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I'm reading the Book Java Concurrency in Practice . In chapter 15, they are talking about the nonblocking algorithms and the compare-and-swap (CAS) method. It is written that CAS perform much better than the locking methods. I want to ask the people who already worked with both of these concepts and would like to hear when you are preferring which one of these concepts? Is it really so much faster? For me, the usage of locks is much clearer and easier to understand and maybe even better to maintain (please correct me if I am wrong) . Should we really focus on creating our concurrent code

Is x86 CMPXCHG atomic, if so why does it need LOCK?

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The Intel documentation says This instruction can be used with a LOCK prefix to allow the instruction to be executed atomically. My question is Can CMPXCHG operate with memory address? From the document it seems not but can anyone confirm that only works with actual VALUE in registers, not memory address? If CMPXCHG isn't atomic and a high level language level CAS has to be implemented through LOCK CMPXCHG (with LOCK prefix), what's the purpose of introducing such an instruction at all? You are mixing up high-level locks with the low-level CPU feature that happened to be named LOCK . The high

Is x86 CMPXCHG atomic, if so why does it need LOCK?

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问题 The Intel documentation says This instruction can be used with a LOCK prefix to allow the instruction to be executed atomically. My question is Can CMPXCHG operate with memory address? From the document it seems not but can anyone confirm that only works with actual VALUE in registers, not memory address? If CMPXCHG isn\'t atomic and a high level language level CAS has to be implemented through LOCK CMPXCHG (with LOCK prefix), what\'s the purpose of introducing such an instruction at all? 回答1

Java Concurrency: CAS vs Locking [closed]

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问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 2 years ago . I\'m reading the Book Java Concurrency in Practice . In chapter 15, they are talking about the nonblocking algorithms and the compare-and-swap (CAS) method. It is written that CAS perform much better than the locking methods. I want to ask the people who already worked with