Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 249ede976fcc5b1fe61e87eb10f64c00aabb1d76
https://github.com/WebKit/WebKit/commit/249ede976fcc5b1fe61e87eb10f64c00aabb1d76
Author: Justin Michaud <[email protected]>
Date: 2026-09-09 (Wed, 09 Sep 2026)
Changed paths:
M Source/JavaScriptCore/heap/Heap.cpp
M Source/JavaScriptCore/runtime/JSLock.cpp
M Source/WTF/WTF.xcodeproj/project.pbxproj
M Source/WTF/wtf/CMakeLists.txt
M Source/WTF/wtf/LockAlgorithmInlines.h
A Source/WTF/wtf/SpinBackoff.h
M Source/WTF/wtf/WordLock.cpp
M Source/WTF/wtf/posix/ThreadingPOSIX.cpp
M Source/bmalloc/CMakeLists.txt
M Source/bmalloc/bmalloc.xcodeproj/project.pbxproj
M Source/bmalloc/bmalloc/Mutex.cpp
A Source/bmalloc/bmalloc/SpinBackoff.h
Log Message:
-----------
Replace sched_yield with nanosleep and abstract away spin lock logic on all
platforms
https://bugs.webkit.org/show_bug.cgi?id=321012
Reviewed by Yusuke Suzuki.
sched_yield is not so helpful, since it isn't guaranteed
to actually yield (unlike the macOS thread_switch) and can
cause deadlocks.
Darwin's tier setup remains mostly unchanged:
Tier 1: spinloop
Tier 2: thread_switch
Tier 3: Parking lot if available (i.e, nothing for bmalloc)
or
Tier 1: spinloop
Tier 2A: pause (avoid hammering the cache)
Tier 2B: thread_switch
(depending on the location)
Linux now has:
Tier 1: spinloop
Tier 2: waiting with backoff to avoid hammering the cache
Tier 3: parking lot OR thread_yield
Thread::yield now definitely always yields, but it is slower.
We acomplish this by making SpinBackoff, which abstracts this logic
away.
We then extend it to a few other places for consistency.
This is measured to be perf-neutral on MBA M4, Neoverse N1 (linux) and RPI4/5
64-bit.
* Source/JavaScriptCore/heap/Heap.cpp:
(JSC::Heap::clearConcurrentRetainedDataIfPossible):
* Source/JavaScriptCore/runtime/JSLock.cpp:
(JSC::JSLock::grabAllLocks):
* Source/WTF/WTF.xcodeproj/project.pbxproj:
* Source/WTF/wtf/CMakeLists.txt:
* Source/WTF/wtf/LockAlgorithmInlines.h:
(WTF::Hooks>::lockSlow):
* Source/WTF/wtf/SpinBackoff.h: Added.
(WTF::SpinBackoff::shouldParkAfterSpinOnce):
(WTF::SpinBackoff::spinOnce):
* Source/WTF/wtf/WordLock.cpp:
(WTF::WordLock::lockSlow):
(WTF::WordLock::unlockSlow):
* Source/WTF/wtf/posix/ThreadingPOSIX.cpp:
(WTF::Thread::yield):
* Source/bmalloc/CMakeLists.txt:
* Source/bmalloc/bmalloc.xcodeproj/project.pbxproj:
* Source/bmalloc/bmalloc/Mutex.cpp:
(bmalloc::Mutex::lockSlowCase):
(bmalloc::yield): Deleted.
* Source/bmalloc/bmalloc/SpinBackoff.h: Added.
(bmalloc::SpinBackoff::shouldParkAfterSpinOnce):
(bmalloc::SpinBackoff::spinOnce):
(bmalloc::SpinBackoff::cpuPause):
(bmalloc::SpinBackoff::platformYield):
(bmalloc::SpinBackoff::yield):
Canonical link: https://commits.webkit.org/320724@main
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