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Bug 5442 - [PATCH] Optimize and fix spinlock behavior for Windows on ARM
Summary: [PATCH] Optimize and fix spinlock behavior for Windows on ARM
Status: RESOLVED FIXED
Alias: None
Product: SDL
Classification: Unclassified
Component: atomic (show other bugs)
Version: HG 2.0
Hardware: ARM Windows 10
: P2 normal
Assignee: Sam Lantinga
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2021-01-03 18:24 UTC by Cameron Gutman
Modified: 2021-01-03 18:36 UTC (History)
0 users

See Also:

Attachments
Patch (1.50 KB, patch)
2021-01-03 18:25 UTC, Cameron Gutman 		Details | Diff
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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