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fix(host/windows): retry DuplicateOutput1 to ride out the old-dup teardown race

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User's insight, and it fits the evidence exactly: in duplicate_output the FIRST
DuplicateOutput1 (called microseconds after the caller releases the old
duplication via self.dupl=None) returns E_ACCESSDENIED, but the legacy
DuplicateOutput a beat later SUCCEEDS — the only difference is TIMING. The
kernel-side teardown of the just-released duplication is async, so the immediate
DuplicateOutput1 races it ('output still duplicated' -> E_ACCESSDENIED). We then
fell straight through to legacy DuplicateOutput, which 'succeeds' into a FRAGILE
dup that churns ACCESS_LOST/MODE_CHANGE every few ms on this cross-GPU IDD
(causing the post-login freeze + UAC-confirm drop).

Fix: retry DuplicateOutput1 up to 5x with escalating 2/4/8/16 ms waits before
falling back to legacy, so the teardown finishes and the ROBUST DuplicateOutput1
dup succeeds (no churn). Bounded (~30 ms worst case) so a genuine failure still
falls back quickly. This is exactly Apollo's 2x/200ms retry rationale.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Enrico Bühler
2026-06-16 16:02:22 +00:00
parent 1e1e5ce9b5
commit eb451d8bc6
1 changed files with 31 additions and 5 deletions
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crates/punktfunk-host/src/capture/dxgi.rs
+31 -5
View File
@@ -186,12 +186,38 @@ unsafe fn duplicate_output(
// wrongly tripping the HDR path. Real HDR capture (FP16 first + IDXGIOutput6 colorspace
// detection to pick the path) is the follow-up once the churn is settled.
let formats = [DXGI_FORMAT_B8G8R8A8_UNORM];
match output5.DuplicateOutput1(device, 0, &formats) {
Ok(d) => return Ok(d),
Err(e) => tracing::warn!(
// RETRY DuplicateOutput1. The caller releases the OLD duplication (self.dupl = None) immediately
// before calling us, and the kernel-side teardown of that duplication is ASYNC — the FIRST
// DuplicateOutput1 right after can race it and return E_ACCESSDENIED ("output still duplicated")
// even though we dropped our only reference. A few short retries let the teardown finish so the
// ROBUST DuplicateOutput1 dup succeeds, instead of falling through to legacy DuplicateOutput,
// which "succeeds" into a fragile dup that churns ACCESS_LOST/MODE_CHANGE every few ms on this
// cross-GPU IDD. (This is why DuplicateOutput1 failed but the legacy call a beat later
// succeeded — pure timing. Apollo retries DuplicateOutput1 2x/200ms for the same reason.)
let mut last_err = None;
for attempt in 0..5u64 {
match output5.DuplicateOutput1(device, 0, &formats) {
Ok(d) => {
if attempt > 0 {
tracing::info!(attempt, "DuplicateOutput1 succeeded on retry (raced old-dup teardown)");
}
return Ok(d);
}
Err(e) => {
last_err = Some(e);
// Escalating brief waits: 2,4,8,16 ms (skip after the last attempt). Bounded so a
// GENUINE failure still falls back to legacy quickly (~30 ms worst case).
if attempt < 4 {
std::thread::sleep(Duration::from_millis(2u64 << attempt));
}
}
}
}
if let Some(e) = last_err {
tracing::warn!(
error = %format!("{e:?}"),
"DuplicateOutput1 failed — falling back to legacy DuplicateOutput"
),
"DuplicateOutput1 failed after retries — falling back to legacy DuplicateOutput (will churn)"
);
}
}
output.DuplicateOutput(device).context("DuplicateOutput")