Archive for category: Multithreading – Memory Model

relaxed

Relaxed Semantics

July 27, 2016

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The relaxed semantics is the end of the scale. The relaxed semantic is the weakest of all memory models…

acquireOperation

Acquire-Release Fences

July 21, 2016

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Acquire and release fences guarantee similar synchronization and ordering constraints as atomics with…

FullFence

Fences are Memory Barriers

July 19, 2016

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The key idea of a std::atomic_thread_fence is to establish synchronization and ordering constraints between…

acquireReleaseWithWaiting

Acquire-Release Semantics – The Typical Misunderstanding

July 16, 2016

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A release operation synchronizes-with an acquire operation on the same atomic variable. So we can easily…

trans

Transitivity of the Acquire-Release Semantic

July 12, 2016

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A release operation synchronizes with an acquire operation on the same atomic variable and establishes,…

acquireReleaseConsume

memory_order_consume

July 9, 2016

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std::memory_order_consume is the most legendary of the six memory models. That's for two reasons. On…

criticalRegion

Acquire-Release Semantic

July 4, 2016

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With the acquire-release semantics, the memory model gets very thrilling. Because now, we do not have…

producerConsumer

Sequential Consistency applied

July 2, 2016

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I have introduced In the post Sequential Consistency the default memory model. This model, in which all…

atomicOperationsReadWriteEng

Synchronization and Ordering Constraints

June 28, 2016

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In this post, our tour through the c++ memory model goes one step deeper. Until now, the posts were only…

Atomics

June 22, 2016

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In addition to booleans, there is atomics for pointers, integrals, and user-defined types. The rules…

Latest news

A Lock-Free Stack: Atomic Smart PointerFebruary 17, 2025 - 11:47 am
The easiest way to solve this memory leak issue from the last post is to use a std::shared_ptr. Atomic Smart Pointer There are two ways to apply atomic operations on a std::shared_ptr: In C++11, you can use the free atomic functions on std::shared_ptr. With C++20, you can use atomic smart pointers. C++11 Using atomic operations […]
A Lock-Free Stack: A Complete ImplementationFebruary 10, 2025 - 3:01 pm
My last lock-free stack implementation was incomplete. It only supported push operations. Let’s change this. The following paragraph about sequential consistency is optional. You can easily ignore it. Sequential Consistency In my examples, I use the default memory ordering: sequential consistency. The reason is simple. Sequential consistency provides the strongest guarantees of all memory ordering […]
My Next Mentoring Program: “Generic Programming (Templates) with C++” startsFebruary 4, 2025 - 4:51 pm
My next mentoring program, “Embedded Programming with Modern C++,” starts on January 31st. Registration is open. Here are more details. Embedded Programming with Modern C++ The mentoring program consists of 16 stations. You have to invest at least 3 hours per week for each one. This means the program takes four months, and you can […]
A Lock-Free Stack: A Simplified ImplementationFebruary 3, 2025 - 10:37 am
Today, I continue my mini story about lock-free data structures. General Considerations From the outside, the caller’s responsibility (application) is to protect the data. From inside, the data structure is responsible for protecting itself. A data structure that protects itself so a data race cannot appear is called thread-safe. First, what general considerations must you […]
Deferred Reclamation in C++26: Read-Copy Update and Hazard PointersJanuary 27, 2025 - 12:23 pm
Before I dive into lock-free programming, there’s a little bit of theory necessary. A common problem in concurrency is the so-called ABA problem. That means you read a variable twice, which returns the same value each time, A. Therefore, you conclude that nothing changed in between. But you forgot the B. Let me first use […]
std::format ExtensionJanuary 20, 2025 - 11:55 am
Displaying the address of an arbitrary pointer in C++ 20 fails but succeeds with C++26. C++20 Only void, const void, and std::nullptr_t pointer types are valid. If you want to display the address of an arbitrary pointer, you must cast it to (const) void*. // formatPointer20.cpp #include <format> #include <iostream> #include <string> int main() { […]