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common: retry early UMWAIT wakes until the Event deadline - #137
#120 fixed the MWAITX path of Event::WaitFor and added src/tests/common/event.cpp. Intel CPUs with WAITPKG (Alder Lake and later) take the UMWAIT path instead, and 7 of the 11 Event tests fail there. On an i9-12900K, WaitFor(2s) returns false while another thread sets the event, and the event stays set afterwards. Unsignalled timed waits of 2 ms to 500 ms return after 0.09 to 1.3 ms.
Cause
The UMWAIT path did if (!is_set.load() && !_umwait(0, end)) return false;. _umwait returns CF, which is set only when the OS limit in IA32_UMWAIT_CONTROL ended the wait. Every other wake returned "timed out" without looking at the event:
A store to the monitored line (a Set during the wait) was reported as a timeout and left the event set.
An interrupt ended the wait early.
The fallback for CPUs with neither MONITORX nor WAITPKG returned true whether or not the event was set.
Fix
UMWAIT now retries until the steady_clock deadline, the same way common: retry unsignalled MWAITX wakes until the Event deadline #120 does for MWAITX. It uses the same bounded cycle budget (MwaitxTimeoutCycles), so the absolute TSC deadline can't wrap for nanoseconds::max().
The deadline and the remaining() helper move up so all three paths share them. The MWAITX path is otherwise unchanged.
The fallback sleeps until the same deadline and returns whether it consumed the event.
Testing
On an i9-12900K (WAITPKG, no MONITORX), Windows 11:
tests.exe "[event]": 7 of 11 failed before, all 11 pass after, over three runs. With the WAITPKG path forced off by a temporary switch (not in this PR), the fallback passes all 11 too.
tests.exe: 665 of 668. The 3 failures are the known ones (nx2_video_render.cpp:151, :210, nup_writer.cpp:671).
Ocarina of Time, outside Link's house, 36 s of consecutive frames per run. Old vs new wait on one binary (temporary switch), four interleaved rounds each. 0 white flashes in every run, fps 48.8 (old) vs 46.8 (new) on average. Individual runs ranged from 31 to 60 fps, so that difference is noise.
The two callers are CoreTiming's HostTiming thread and the audio renderer's shutdown wait. Neither showed a visible change in-game.
Notes
Not tested on AMD. The MWAITX path only moved its deadline out to share it.
Windows on ARM has its own WaitFor with the same always-true fallback. It's untouched here because I can't test it.
zortos293#120 fixed the MWAITX path of Event::WaitFor and added the Event tests.
Intel CPUs with WAITPKG (Alder Lake and later) take the UMWAIT path
instead, and 7 of the 11 Event tests fail there (i9-12900K).
UMWAIT's result (CF) is set only when the OS limit in IA32_UMWAIT_CONTROL
ended the wait. Every other wake (a store to the monitored line, an
interrupt, the deadline) returned "timed out" without looking at the
event. A Set during the wait was reported as a timeout and left the
event set, and an interrupt ended the wait early.
Retry until the steady_clock deadline the way the MWAITX path does, with
the same bounded cycle budget so the absolute TSC deadline can't wrap.
The fallback for CPUs with neither instruction returned true even when it
timed out. It now waits for the same deadline and returns whether it
consumed the event.
Tested on an i9-12900K (WAITPKG, no MONITORX), Windows 11:
- tests.exe "[event]": 7 of 11 failed before, all pass after (three
runs). With the WAITPKG path forced off by a temporary switch (not in
this commit), the fallback passes them too.
- tests.exe: 665 of 668, the 3 known failures.
- Ocarina of Time outside Link's house, old vs new wait on one binary,
four interleaved rounds each: 0 flashes in every run, 48.8 vs 46.8 fps
on average, within run-to-run noise (31 to 60 fps).
Not tested: the MWAITX path (AMD) only moved its deadline out to share
it. Windows on ARM has its own WaitFor with the same always-true
fallback, untouched here.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
On x86-64 Windows, Event::WaitFor uses a steady-clock deadline across MWAITX, WAITPKG, and polling. WAITPKG recalculates its wait budget after early wakes. The polling fallback returns whether it consumed the signaled state.
Changes: Windows event wait handling
Layer / File(s)
Summary
Shared deadline and wait outcomes src/common/thread.cpp
MWAITX, WAITPKG, and the polling fallback use a shared steady-clock deadline. WAITPKG retries after early wakes and returns false when the deadline expires. The fallback reports whether it consumed the signal.
zortos293/Lichii#120: Changes the same Common::Event::WaitFor implementation and adds the deadline and MWAITX budget that this PR extends.
Suggested reviewers:zortos293
Merge Risk: Minimal · up to 3e756
Early wakes are retried, and no actionable merge-blocking risk was identified.
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The title names the main change: Event::WaitFor on UMWAIT now retries early wakes until the steady_clock deadline. The PR objectives confirm this is the central fix, and the raw summary describes the …
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The title names the main change: Event::WaitFor on UMWAIT now retries early wakes until the steady_clock deadline. The PR objectives confirm this is the central fix, and the raw summary describes the WAITPKG path recomputing a bounded wait budget after early wakeups until the deadline expires. The title is specific and concise, and it does not describe anything absent from the changeset.
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…os293#137, zortos293#141)
Conflicts kept both sides: upstream's indirect storage handle reads with
our host-aligned base (shader_handle_program.h), upstream's query DMA
trace with our query-write wait (macro.cpp, vk_rasterizer.cpp), and both
includes in maxwell_3d.cpp.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
chrispository
pushed a commit
to chrispository/MyLichii
that referenced
this pull request
Nov 7, 2026
)
zortos293#120 fixed the MWAITX path of Event::WaitFor and added the Event tests.
Intel CPUs with WAITPKG (Alder Lake and later) take the UMWAIT path
instead, and 7 of the 11 Event tests fail there (i9-12900K).
UMWAIT's result (CF) is set only when the OS limit in IA32_UMWAIT_CONTROL
ended the wait. Every other wake (a store to the monitored line, an
interrupt, the deadline) returned "timed out" without looking at the
event. A Set during the wait was reported as a timeout and left the
event set, and an interrupt ended the wait early.
Retry until the steady_clock deadline the way the MWAITX path does, with
the same bounded cycle budget so the absolute TSC deadline can't wrap.
The fallback for CPUs with neither instruction returned true even when it
timed out. It now waits for the same deadline and returns whether it
consumed the event.
Tested on an i9-12900K (WAITPKG, no MONITORX), Windows 11:
- tests.exe "[event]": 7 of 11 failed before, all pass after (three
runs). With the WAITPKG path forced off by a temporary switch (not in
this commit), the fallback passes them too.
- tests.exe: 665 of 668, the 3 known failures.
- Ocarina of Time outside Link's house, old vs new wait on one binary,
four interleaved rounds each: 0 flashes in every run, 48.8 vs 46.8 fps
on average, within run-to-run noise (31 to 60 fps).
Not tested: the MWAITX path (AMD) only moved its deadline out to share
it. Windows on ARM has its own WaitFor with the same always-true
fallback, untouched here.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
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Problem
#120 fixed the MWAITX path of
Event::WaitForand addedsrc/tests/common/event.cpp. Intel CPUs with WAITPKG (Alder Lake and later) take the UMWAIT path instead, and 7 of the 11 Event tests fail there. On an i9-12900K,WaitFor(2s)returns false while another thread sets the event, and the event stays set afterwards. Unsignalled timed waits of 2 ms to 500 ms return after 0.09 to 1.3 ms.Cause
The UMWAIT path did
if (!is_set.load() && !_umwait(0, end)) return false;._umwaitreturns CF, which is set only when the OS limit inIA32_UMWAIT_CONTROLended the wait. Every other wake returned "timed out" without looking at the event:Setduring the wait) was reported as a timeout and left the event set.The fallback for CPUs with neither MONITORX nor WAITPKG returned
truewhether or not the event was set.Fix
steady_clockdeadline, the same way common: retry unsignalled MWAITX wakes until the Event deadline #120 does for MWAITX. It uses the same bounded cycle budget (MwaitxTimeoutCycles), so the absolute TSC deadline can't wrap fornanoseconds::max().remaining()helper move up so all three paths share them. The MWAITX path is otherwise unchanged.Testing
On an i9-12900K (WAITPKG, no MONITORX), Windows 11:
tests.exe "[event]": 7 of 11 failed before, all 11 pass after, over three runs. With the WAITPKG path forced off by a temporary switch (not in this PR), the fallback passes all 11 too.tests.exe: 665 of 668. The 3 failures are the known ones (nx2_video_render.cpp:151,:210,nup_writer.cpp:671).The two callers are
CoreTiming's HostTiming thread and the audio renderer's shutdown wait. Neither showed a visible change in-game.Notes
WaitForwith the same always-true fallback. It's untouched here because I can't test it.🤖 Generated with Claude Code
Summary by CodeRabbit