This time, we take a stab at implementing Hazard Pointers (https://erdani.org/publications/cuj-2004-12.pdf) in Rust. We follow along with the C++ implementation in Facebook’s Folly library (https://github.com/facebook/folly/blob/master/folly/synchronization/Hazptr.h), as well as the C++ standardization proposal (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p1121r3.pdf).

• 0:00:00 Introduction
• 0:00:37 Rust for Rustaceans
• 0:01:00 Concurrent Memory Reclamation
• 0:10:32 Hazard Pointers
• 0:35:27 Folly’s Hazard Pointer Interface
• 0:54:08 Delayed Reclamation
• 0:58:18 More Folly Interface
• 1:11:56 A Wild Entity Diagram Appears
• 1:16:40 Memory Use
• 1:21:12 More Folly Interface
• 1:27:50 Starting the Rust Code
• 1:35:24 Testing Out the Rust Interface
• 1:42:32 HazPtrHolder::load
• 2:02:15 HazPtrObject::retire
• 2:19:43 HazPtrHolder::reset
• 2:22:50 Unsafe Blocks in Unsafe Fns
• 2:25:04 Borrow Checker Prevents Misuse
• 2:27:45 Bad Drop Lint
• 2:34:15 Dropping in HazPtrDomain::retire
• 2:46:00 Intermission
• 2:47:57 Reading Folly’s HazPtrDomain::retire
• 2:59:02 HazPtrDomain::acquire
• 3:17:32 HazPtrDomain::retire
• 3:45:57 Specifying a Deleter
• 4:32:26 Tests Pass?
• 4:36:12 Eager Reclaiming
• 4:37:32 Checking Reclamation Behavior
• 4:52:04 Final Thoughts

You can find the code for the implementation at https://github.com/jonhoo/haphazard.

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