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Bug 5442

Summary: [PATCH] Optimize and fix spinlock behavior for Windows on ARM
Product: SDL Reporter: Cameron Gutman <cameron.gutman>
Component: atomicAssignee: Sam Lantinga <slouken>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2    
Version: HG 2.0   
Hardware: ARM   
OS: Windows 10   
Attachments: Patch

Description Cameron Gutman 2021-01-03 18:24:54 UTC 
The current implementation of SDL_AtomicUnlock() is not safe for Windows on ARM because it only enforces a compiler memory barrier before unlocking, rather than a real hardware memory barrier.

There's also a little optimization opportunity in SDL_AtomicTryLock() too, since using the InterlockExchange variant with acquire semantics is faster on ARM since it avoids generating a 'dmb' instruction.
Comment 1 Cameron Gutman 2021-01-03 18:25:36 UTC 
Created attachment 4635 [details]
Patch
Comment 2 Sam Lantinga 2021-01-03 18:36:22 UTC 
Patch added, thanks!
https://hg.libsdl.org/SDL/rev/1cfb48c58bbd