Reclamation Beyond Concurrency TS2 – Maged Michael Protector Remover / Reclaimer Hazard pointers protect access to objects that may be removed concurrently. SAFE RECLAMATION Concurrency TS2 Essential Hazard make_hazard_pointer(); Hazard Pointer Synchronous Reclamation Beyond Concurrency TS2 – Maged Michael See N4895 (wg21.link/n4895) for working draft of Concurrency TS2 Example Using Hazard Pointers class Foo : public Shared data, frequently-used, infrequently-updated Hazard Pointer Synchronous Reclamation Beyond Concurrency TS2 – Maged Michael Why use hazard pointers? • Fast (low nanoseconds) and scalable protection.

operation 5. Implementing a simple algorithm 6. Senders and coroutines Part 2: 1. Structured concurrency 2. Cancellation 3. An extended example3 GOALS FOR THE EXECUTORS PROPOSAL The vision: “An asynchronous use coroutines or not in the hands of the caller.51 COMING UP IN THE NEXT HOUR: Structured concurrency Cancellation support in sender/receiver Extended example: Sender/receiver and ranges52 ADDITIONAL WHAT’S COMING IN PART 2 1. Structured concurrency 2. Cancellation support in the sender/receiver abstraction 3. An extended example56 Structured concurrency57 IN THE BEGINNING … WAS GOTO From: “Go

danielanderson.net What we’ll learn today • How shared_ptr is implemented under the hood • Atomics and concurrency patterns • How existing atomic are implemented (the split reference count technique) danielanderson.net What we’ll learn today • How shared_ptr is implemented under the hood • Atomics and concurrency patterns • How existing atomic are implemented (the split reference count technique) open-source library, used in production), • Used by JustThreads (Anthony Williams’ commercial concurrency library), • Anthony Williams also has a free, simplified version on GitHub • Other implementations

functions  union, try/catch, dynamic_cast, typeid  allocations  constexpr string & vector  Concurrency Changes  Atomic Smart Pointers  Joining & Cancellable Threads  The C++20 Synchronization Library Features: One Year of Development on GitHub” -- Stephan T. Lavavej Tuesday, September 15 • 13:30Concurrency Changes35 Atomic Smart Pointers  Is shared_ptr thread safe?  Yes: control block manipulation the thread counter is reset  the next phase starts  threads can continue “Back to Basics: Concurrency” -- Arthur O'Dwyer Friday, September 18 • 10:3044 The C++20 Synchronization Library  Waiting

Fusion of IO/CPU intensive 结构化并发 Structured Concurrency 核心在于通过一种父子结构化的方法实现并发程序，用具有明确入口点和出口 点的控制流结构来封装并发任务（可以是线程也可以是协程）的执行，确保所有派生任务在出口之前完 成。 Structured concurrency 结构化并发带来的好处：  更高的易用性，用户不再需要显示调用 await   提高程序的可读性和可维护性  保证了变量生命周期合法，使子任务可以捕获父任务的变量 结构化并发 Structured concurrency Scope  Rust 线程中的结构化并发  阻塞等待所有 Scope 内的子线程任务完成  子线程执行的闭包中可以捕获 Scope 外的变 量 AsyncScope  将 std 库中 thread scope 的思想异步化 

increasingly gaining attention from developers. With its impressive performance, memory safety, and concurrency features, Rust has become an ideal choice for building high-performance mobile applications.

Path-Sensitive Dataflow Analysis with Iterative RefinementMSVC has both Path-sensitive • Use after move • Concurrency checks • Variant clear • Enum Index • HResult • Nullptr dereference • more to come.. Flow-sensitive

Rust is a multi-paradigm programming language focused on performance and safety, especially safe concurrency. empty • vmm-vcpu: a hypervisor-agnostic abstraction for Virtual CPUs (vCPUs). rust-vmm • event-manager:

memory-efficient • No runtime or garbage collector Reliability • Guaranteed memory safety • “Fearless Concurrency” Productivity • Modern development tools • Lots of amazing libraries Rust 编译通过了 bug 比 cpp 少上

已经非空，则可以不用上锁，减少上锁次数。 如果 block 为空，则上锁；再次检测是否为空，空则分配内存， 非空说明其他线程已经帮我分配好了，直接退出。 结果反而还变慢了……所以有时候教科书（如 Concurrency in Action ）不一定就是完美解决方案，要根据实际情况判断。 真正的解决： tbb::spin_mutex 其实主要的瓶颈在于 std::mutex 会切换到操作系统内核中去调度