基于RISC-V原子指令重构并发模块 (Concurrency Module Refactoring Using RISC-V Atomic Instructions)#163
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FlandreLiao wants to merge 14 commits intorcore-os:ch8from
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基于RISC-V原子指令重构并发模块 (Concurrency Module Refactoring Using RISC-V Atomic Instructions)#163FlandreLiao wants to merge 14 commits intorcore-os:ch8from
FlandreLiao wants to merge 14 commits intorcore-os:ch8from
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- Refactor mutex module architecture - Add new MutexSpin and Futex implementations using atomic instructions - Introduce Futex support with following additions: * Atomic operations: increment/decrement/bit_test_set/add_and_compare * System Call: sys_futex * PCB member: futex_queues * MemorySet method: translation_va Todo: test the correctness of new Mutex
- Copy MutexSpin to user lib - Cut Futex from os/sync/mutex.rs to user lib - delete some mutex syscalls Todo: test the correctness of new Mutex Todo: reconstruct Condvar
…ser crate - Delete syscalls of Condvar - Add new Condvar based on sys_futex to user lib Todo: Examine correctness of Mutex and Condvar
Store in , not .
- Return val & (1 << bit)
- Move semaphore module from kernel to user lib - Delete semaphore syscalls
Now Semaphore is like to Zemaphore
FlandreLiao
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问题描述
原来的并发模块严重依赖内核态的中断屏蔽机制，导致同步原语相关的系统调用多达数十个，不仅使内核与用户程序的 接口臃肿冗余，还大大增加了同步原语的性能开销。另外，同步原语的数据结构 只定义在于内核中，不对用户程序开放，使得用户程序只能使用语义不明的 ID 作为同步原语的句柄。
新的并发模块概述
用户态（或者说 user_lib 中）实现了 MutexSpin, Futex, Condvar, Semaphore 四种同步原语，内核态只实现了 MutexSpin。
与原来的并发模块相比，新的并发模块的系统调用数量从 10 个削减到仅剩 1 个，精简了内核接口。自旋锁基于原子指令实现，相比于中断屏蔽大大提高了性能；Futex 在用户态的检查操作同样基于原子指令，仅在必要时通过 sys_futex 进入内核态；Condvar 和 Futex 复用了 sys_futex；Semaphore 基于 MutexSpin 和 Condvar 实现。
