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perf(ffi): poll-native async for kio-backed reads - #7497
Every moq-ffi read over kio-backed state went through ffi::Task. Each call took a tokio Mutex, subscribed to a watch cancel flag, and polled a select! against shutdown. That cost time on the hot read path. A read that the binding cancelled but has not freed yet (Kotlin and Swift leave this window open between rust_future_cancel and rust_future_free) also held the lane, so the next read on the same handle blocked behind it. The spike measured Shape A as the fix, and the maintainer settled on it on 2026-10-16.
Approach
ffi::Polled<T> replaces Task on every export that only polls its handle's state. Each call is a kio::wait, which UniFFI's RustFuture polls directly. Each poll:
runs inside shutdown's in-flight accounting and the runtime context, so a poll that missed shutdown finishes before shutdown returns, and a tokio timer in the state (the media consumer's hole timer) stays pollable;
parks on the runtime's stop signal, which is now a kio channel, so a parked call resolves Cancelled once shutdown runs;
checks the owner driver through the new Background::poll_failed, then a cancel channel, then locks the state for that one poll only.
The state sits behind a kio::Bridge. Each call holds its own kio::Park against the bridge's context, so its waiter wakes through the bridge's one waker, which wakes every call parked on the handle. moq-net's track cursor keeps one waker per read (track::idle::Idle), so without the bridge only the latest caller would wake. The bridge also holds back any wake sent while the state is locked until the lock is released. UniFFI runs the foreign continuation on the waking thread, so a binding may poll the woken call right there, and it must not find the state still locked.
cancel() closes the channel, then drops the state before it returns, inside the runtime. A panic during that drop is reported by later calls instead of unwinding into the caller. Concurrent calls on one handle all park, and each poll takes the next item atomically.
read_frame on a track runs its whole step in one poll: acquire the next group if pending is empty, then read its first frame. If another call took the group between polls, the next poll acquires a new one. A group still waiting on its first frame stays in pending, so a cancelled read_frame still leaves it for next_group. When next_group takes a group out of pending, it wakes the bridge, so a read_frame parked on that group moves on.
Shutdown's in-flight count is now an atomic with a stop bit. Before, it took a global mutex twice per poll, on the Task path as well. A condvar is used only for the last poll that shutdown waits for.
drive codecs; cancelling a queued video decode poisons its sink
MoqTrackDemand::wanted_changed
kept detached
demand wait, per the Plan
MoqFill::unwanted
kept detached
demand wait for one group of a fill
MoqTokens::answered
kept detached
waits for the peer's AUTH answer; never went through Task
MoqSession::shutdown
kept spawned (ffi::spawn)
the drain must outlive the handle and any closed() waiter
Task::take lost its last caller and is removed.
Impact
Public API: no signature changes. Concurrent calls on one handle no longer get items in call order; sequence and arrival order are unchanged. A cancelled but unfreed call no longer delays the next one. cancel() on the migrated handles releases the state before it returns, where before a task did that later. Recorded in the moq-ffi CHANGELOG.
Wrapper docs: none of them promise serialized reads (checked Go, Python, Kotlin, Swift, Dart, and doc/), so none change.
Wire: none.
Choices made without asking
Migrated every pure-kio export the Plan's rule covers, beyond the Goal's examples: origin and track request waits, fill changes, grants, and bandwidth.
MoqGroupConsumer handed to MoqMediaGroupConsumer::new still fails with Busy while a read is in flight, counted by Polled::busy. That keeps today's behavior.
MoqOriginRequests::requested_broadcast after cancel() still returns Closed, and a parked call still returns Cancelled, as before.
One poll covers the whole read_frame step: acquire, or re-acquire when the slot is empty, then read. This is one of the options the Plan offered.
The shutdown counter is now atomic, and the stop signal is a kio channel shared by Task and Polled.
Polled bridges every handle, not only the track, which is the one known to keep a single waker. The cost is that any progress on a handle wakes all of its parked calls, so a datagram can wake a parked group read. Bridging every handle keeps every handle correct without auditing each inner type's waker policy.
Land ejection (2026-11-01)
The land queue ejected this PR twice with test rs failing. The first failure was the moq_clock to kio::clock rename, which the land fixer already handled. The second was this PR's own raw_track_concurrent_reads_take_every_group_once, which hung in most runs on the pre-merge head d60a595f69 (it failed the first of 40 stress iterations). Only one of its four readers ever woke, because moq-net's track cursor keeps one waker and each concurrent call replaced the last one's. Neither moq-dev/moq#7506 nor anything else from main caused it. Now that #7506 has landed, moq-ffi gets kio's async feature through moq-net and needs no manifest change.
Fixed by bridging Polled (above). The same change fixes CodeRabbit's finding that next_group woke parked read_frame calls while still holding the state lock. A binding that polls inline would deadlock there, and raw_next_group_wakes_read_frame_after_unlocking timed out before the fix.
Fit with the exporter switch (2026-11-02)
On 2026-11-02 the maintainer decided that moq's bindings will switch to rust2's exporter rather than a UniFFI fork (moq-dev/moq#7648, quest/m2/ffi-exporter.md). That decision leaves this quest in place: the same commit kept quest/m2/ffi-poll-migrate.md and re-pointed its "no UniFFI change" link at the exporter switch.
Once the switch lands, the exporter exports moq-net's own poll_* API and moq-ffi shrinks to genuinely new API. At that point Polled and these export bodies go away. Until then, the shipped bindings get the throughput gain and lose the read lane, so a cancelled but unfreed read no longer blocks the next one. The switch is still blocked on rust2's exporter epic and its five open children. The semantics here (no lane, concurrent reads each take the next item, a cancel ends only that read) match what the exporter's generators plan. Work outside moq-ffi survives the switch: Background::poll_failed, the atomic shutdown counter, and the tests that pin those semantics.
Merge with main (2026-11-03)
Merged origin/main at e25f6266df, no rebase. Main made frame timestamps exact (MoqTimestamp, moq-dev/moq#6946), so raw_frame, media_frame, and the MoqMediaRead conversion became infallible. The polled reads now wrap them in Ok(...) instead of calling transpose(). Main's Task-based bodies for the same exports were dropped in favor of this PR's Polled ones. The quest deletion is kept. Main had added two links to the deleted quest in the no-spawn epic (moq-dev/moq#7519), and this merge removes them. That leaves quest/m1/poll-first/no-spawn/ffi.md with no Required entry, so it is unblocked.
Validation
New tests:
raw_read_frame_moves_on_when_next_group_takes_its_group: a read_frame parked on a frameless group moves on to the next group when next_group takes the one it was waiting on.
UniFFI rust_future_* driven directly: a track read_frame and a group read_frame that are cancelled but not freed don't block the next read on the same handle.
Four reads parked on one track (two read_frame, two next_group, on a multi-thread runtime) take all 200 groups exactly once.
shutdown_waits_for_a_polled_call: a poll in flight when shutdown starts finishes before shutdown returns, a later call is Cancelled, and a call parked across shutdown resolves Cancelled.
Polled unit tests for take, busy, cancel, the cleanup panic, two concurrent calls, and two calls parked on a state that keeps one waker.
raw_next_group_wakes_read_frame_after_unlocking: a read_frame whose waker polls it inline, as an unconfined coroutine would, is woken by next_group after the state is unlocked.
The existing shutdown_cancels_and_drops_cleanly now covers a parked migrated read_frame.
Removed raw_track_pending_group_read_holds_the_lane, since the lane no longer exists.
just ci origin/main passes on head 8b28e429b5 (merged with main at e25f6266df): Rust, Python, Go, Kotlin, Dart, C, C++, OBS, and lint modules. quest check --base origin/main passes.
The track, read_frame, and Polled tests pass 40 of 40 runs under --stress-count 40.
The benchmark below predates the bridge, which adds a few uncontended lock operations per poll. It was not rerun.
Go binding benchmark: the base (origin/main at 2d13685) and head runners were staged once each, then alternated for 5 rounds at -benchtime=2s. The table shows medians. The host was shared with other agents and a single run swung up to 2x, so read these as direction, not magnitude:
case
base
head
change
CPU ms/MB base → head
100 B, 1 pub / 1 sub
16.3 MB/s
20.3 MB/s
+25%
83.7 → 72.6
1 KiB, 1 / 1
131.4 MB/s
162.6 MB/s
+24%
12.6 → 10.6
1 KiB, 1 / 4
174.8 MB/s
468.2 MB/s
+168%
8.9 → 7.5
1 KiB, 4 / 1
97.4 MB/s
153.1 MB/s
+57%
13.7 → 12.2
1 KiB, 4 / 4
231.1 MB/s
513.3 MB/s
+122%
10.2 → 9.6
sequence (sync)
129.9 ns
118.5 ns
-9%
info (sync)
385.3 ns
312.4 ns
-19%
Head is ahead on both fan-out axes, and CPU per MB falls in every throughput case. The sync calls didn't change, so their movement shows the noise floor. The 64 KiB case fails with evicted on base and on head alike, so it is excluded (follow-up below).
Follow-ups
Delete the spike/ffi-poll-prototype branch once this lands, as the Plan says.
The binding benchmark's 64 KiB case fails with evicted on origin/main too: one round's groups outgrow the 64 MiB origin cache budget, or the consumers fall behind its eviction.
A quiet host would give clean benchmark numbers; the rust2 nightly just bench-ffi will report them against its pinned revision.
Review
Reviewer: Codex, gpt-6.1-sol, medium effort (quest review --base origin/main, a new session), head 8b28e429b5058bed60000995a5758f37eaa0aa66.
Round 1 (head 8b28e429b5, the merge with main): no findings.
Previous session, head 3f886d3b27, after the Design change: comment: round 1 (head afce050de0) found that the shared bridged waiter stacked duplicate registrations once a handle had more than eight parked calls. The fix gives each call its own kio::Park. Round 2 had no findings. Before the design change, at head 256438d965, a read_frame parked on a frameless pending group was not woken when next_group took that group. That was fixed and is covered by raw_read_frame_moves_on_when_next_group_takes_its_group.
Online review: CodeRabbit's finding on consumer.rs (a wake sent while the state lock was held) was fixed by the bridge in 3f886d3b27, and CodeRabbit confirmed it in the thread. The OpenAI review of 3f886d3b27 reported no findings. Pullfrog reported no issues. Its failing check is optional and comes from a billing outage, so it was ignored.
No actionable comments were generated in the recent review.
Walkthrough
The FFI replaces task-wrapped reads and waits with direct polling through a new Polled handle. Runtime shutdown now tracks active polls, and track/group reads use updated coordination for pending groups and concurrent calls. Tests cover cancellation, concurrent consumption, group handoff, and shutdown. The changelog records the polling behavior, and the m2 migration plan is removed.
Merge Risk: Minimal · up to 3f886
The poll-native FFI read change no longer has the earlier inline-wake deadlock, because wakes sent under the state lock are now deferred until it is released. No unresolved concrete risk remains from this review, so it looks ready to merge after normal checks.
Pre-merge checks: 5
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Status
Explanation
Title check
The title clearly and concisely identifies the main change: migrating kio-backed FFI reads to poll-native async handling for performance.
Docstring Coverage
Docstring coverage is 85.37% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentati…
Linked Issues check
Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check
Check skipped because no linked issues were found for this pull request.
Description check
The description directly explains the migration from ffi::Task to ffi::Polled, its concurrency and shutdown behavior, affected exports, tests, benchmarks, and follow-up work. It is clearly related …
Full details: Docstring Coverage
Explanation
Docstring coverage is 85.37% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 41 functions across 9 files.
Full details: Description check
Explanation
The description directly explains the migration from ffi::Task to ffi::Polled<T>, its concurrency and shutdown behavior, affected exports, tests, benchmarks, and follow-up work. It is clearly related to the changeset.
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quest/m2/README.md
rs/moq-ffi/src/consumer.rs
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P2 — Defer reader wakes until after unlocking (rs/moq-ffi/src/consumer.rs:464). ordered.readers.wake() runs inside Polled::poll while its state mutex is held. If Kotlin readFrame() is parked on a frameless group using Dispatchers.Unconfined, a nextGroup() call from another ordinary coroutine can synchronously resume that reader through UniFFI’s wake callback. The reader immediately repolls and blocks on the same mutex, so neither call returns. Collect/defer these wakes until after the state guard is released, and cover the pending-group handoff with an inline foreign continuation regression. UniFFI’s scheduler invokes the callback synchronously; its Kotlin async loop resumes and repolls.
Direction: replacing the pure-kio read lanes with direct polling is a useful simplification; retaining Task for I/O/codecs and shutdown accounting is justified. The earlier pending-group missed-wake finding described in the PR is addressed, but its new wake must be reentrancy-safe as above. No other actionable bugs found in the migration and surrounding lifecycle code.
Verification: static review, including an independent concurrency pass; tests, Kotlin reproduction, and benchmarks were not executed.
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✅ No new issues found.
Reviewed changes — I read the full diff and independently verified the two highest-risk areas (the rewritten shutdown accounting and the concurrent read_frame/next_group wake protocol) with source-level reasoning against kio::WaiterList/Pending and moq_net::group semantics.
Polled<T> replaces Task<T> on kio-backed reads — state sits behind a std Mutex held only across one poll; a kio::Producer cancel channel wakes parked calls; Background::poll_failed waits for owner failure; calls/cleanup back busy() and drop-panic reporting. Export signatures are unchanged.
Runtime shutdown accounting — Mutex<Polls> becomes AtomicUsize with a STOPPED high bit plus an idling mutex guarding the idle condvar; the stop signal is now a kio channel shared by Task and Polled. The increment/decrement/notify protocol keeps exactly the "wait until the last pre-STOPPED poll ends" contract, including the transient increment from a failing Polling::start.
TrackInner::poll_read_frame — acquire-or-reacquire plus frame read in one poll; OrderedCursor.readers wakes a read_frame parked on a frameless pending group when next_group takes it. Every pending Some→None transition is covered by either readers.wake() or the group's own state write, so no parked reader is stranded.
Migrations — track/group/datagram, announcements/following, request/fill waits, grant/bandwidth, JSON and media consumers. Task is kept for I/O, codecs, sessions, and server/connect paths; demand waits stay detached. The inventory in the PR body matches the sites I checked.
Tests/docs — new rust_future_*-driven cancelled-unfreed tests, a mixed 200-group concurrent-read test, and a shutdown-in-flight test; quest completion (file + index bullet) and CHANGELOG Unreleased → Changed entry are correct, with no dangling references to the deleted quest.
No line-anchored or cross-cutting concerns to raise.
The auth decider loop and moq-stats' publisher split are in #7360,
and moq-ffi's task plumbing is in #7497. Point at both so this
quest builds on them instead of redoing them.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Actionable comments posted: 1
Fix comments: Fix CodeRabbit comments on this PR
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Inline comments:
Review comments at @rs/moq-ffi/src/consumer.rs:
- Around line 463-464: Move the wake in poll_next_group outside the Polled state
lock, since awakened UniFFI continuations may poll inline and re-enter that
lock. Have poll_next_group report when it takes a pending group, then wake
ordered.readers after Polled::wait releases the state guard; preserve the
existing wake behavior for each taken group.
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rs/moq-ffi/src/auth.rs
rs/moq-ffi/src/bandwidth.rs
rs/moq-ffi/src/consumer.rs
rs/moq-ffi/src/ffi.rs
rs/moq-ffi/src/json.rs
rs/moq-ffi/src/media.rs
rs/moq-ffi/src/origin.rs
rs/moq-ffi/src/producer.rs
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quest/m2/ffi-poll-migrate.md
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codex / Codex land fixer: This maintainer pick already used its mechanical fi·x attempt. Run /quest-iterate to diagnose the repeated failure, then pick it again.
moq-net's track cursor keeps one waker per read, so with several calls
parked on one MoqTrackConsumer only the latest caller ever woke and the
rest hung (raw_track_concurrent_reads_take_every_group_once failed most
runs, which is what ejected this PR from the land queue).
Polled now keeps its state behind a kio::Bridge and always polls it with
the bridge's one waiter, which wakes every parked call. The bridge also
holds a wake sent under its lock until the lock is released, so a binding
that polls a woken call inline cannot deadlock on the state. That covers
next_group waking a read_frame parked on the group it took, so the
track's separate readers list is gone.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
A waiter shared by every call on a handle was never retired, so a call
re-polled by another's wakes past its eight records stacked duplicate
registrations on a list it stayed parked on. Each call now holds its own
kio::Park against the bridge's context: its waiter still wakes through the
bridge's one waker, which one-waker handles need, and retires as usual.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Design change: Polled now keeps its state behind a kio::Bridge, and each call polls the state with its own kio::Park held against the bridge's context.
Why: moq-net's track cursor keeps one waker per read (rs/moq-net/src/model/track/idle.rs). Before this change, every concurrent call on one MoqTrackConsumer replaced the previous call's waker, so only the latest caller ever woke. That is why raw_track_concurrent_reads_take_every_group_once hung and the land queue ejected this PR. The bridge fans one waker out to every parked call. It also holds back wakes sent under the state lock until the lock is released, which fixes CodeRabbit's inline-poll deadlock and replaces the track's separate readers waiter list.
Cost: any progress on a handle now wakes all of its parked calls, plus a few uncontended lock operations per poll. The single-reader path is otherwise the same.
Pullfrog's billing service is temporarily unavailable, so this run didn't start. This is on our side, and nothing was billed. The next run should succeed; if it keeps failing, check status.pullfrog.com.
No new actionable bugs found in the substantive changes since the previous review, separating the main-branch merge from the two bridge fixes.
Prior P2 fixed:consumer.rs:457–463 now wakes the bridge, and ffi.rs:480–483 polls under its guard. kio::Bridge releases the state lock before delivering deferred wakes, addressing the inline-repoll deadlock also independently reported by CodeRabbit. The added inline-waker regression exercises that handoff. The stable bridge waker also prevents concurrent track reads from replacing one another's wake target; each call's own Park (ffi.rs:454–456) retains and retires its registrations independently.
Direction: reusing Bridge and deleting the track-specific readers list is preferable to adding a second deferred-wake mechanism. Its wake-all cost is justified for shared single-waker cursors, with no additional public API or wire change. The pre-bridge benchmark does not establish the final implementation's performance.
Verification: static inspection of the changed polling, cancellation, waiter/bridge lifecycle, track cursor, and regression tests. I did not run tests, foreign-binding reproductions, or benchmarks.
…rate
Adapt the polled reads to main's exact timestamps (raw_frame, media_frame,
and MoqMediaRead conversions are now infallible), keep the quest deletion,
and drop the links main added to it from the no-spawn epic.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
No new actionable issues found. Accounting for main's changes, the timestamp conversion port preserves the polled read results, and the prior deferred-wake fix remains in place.
Static GitHub review only; I did not run tests or benchmarks.
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✅ No new issues found.
Reviewed changes — this increment re-reviewed the commits since the prior Pullfrog review: the kio::Bridge / per-call Park rewrite of Polled and the merge with origin/main.
Polled's state moved behind kio::Bridge with a per-call kio::Park — each call holds its own park against the bridge's single waker, so a state that keeps one waker (moq-net's track cursor) wakes every parked call, and a wake sent while the state is locked is deferred until the lock releases. This is the fix for both the lost concurrent-read wake and the reentrant inline-poll deadlock.
Track wake simplified — the track cursor's readers: kio::WaiterList is gone; next_group wakes the bridge's shared waker when it takes a parked read_frame's group, deferred to after the state lock releases.
New regressions pinned — polled_one_waker_state_wakes_every_parked_call and raw_next_group_wakes_read_frame_after_unlocking (an inline-repolling waker) both pass.
Merge with origin/main — exact MoqTimestamp frames make raw_frame, media_frame, and the MoqMediaRead conversion infallible (.transpose() → Ok(...)), origin follow's epoch parameter is renamed to instance, and the tests moved to the base's kio::clock::timeout / us(...) helpers.
Quest bookkeeping — ffi-poll-migrate.md is deleted and the no-spawn README/ffi links updated, leaving no references to it.
I verified the bridge handoff independently (each call's outer waiter registers in the bridge list before the lock is held; a deferred wake is delivered only after both the waiters mutex and the inner lock drop, so an inline continuation cannot deadlock). A reviewfrog concurrency specialist reached the same conclusion and quoted UniFFI's synchronous scheduler. No line-anchored or cross-cutting concerns to raise.
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Problem
Every moq-ffi read over kio-backed state went through
ffi::Task. Each call took a tokioMutex, subscribed to awatchcancel flag, and polled aselect!against shutdown. That cost time on the hot read path. A read that the binding cancelled but has not freed yet (Kotlin and Swift leave this window open betweenrust_future_cancelandrust_future_free) also held the lane, so the next read on the same handle blocked behind it. The spike measured Shape A as the fix, and the maintainer settled on it on 2026-10-16.Approach
ffi::Polled<T>replacesTaskon every export that only polls its handle's state. Each call is akio::wait, which UniFFI'sRustFuturepolls directly. Each poll:Cancelledonce shutdown runs;Background::poll_failed, then a cancel channel, then locks the state for that one poll only.The state sits behind a
kio::Bridge. Each call holds its ownkio::Parkagainst the bridge's context, so its waiter wakes through the bridge's one waker, which wakes every call parked on the handle. moq-net's track cursor keeps one waker per read (track::idle::Idle), so without the bridge only the latest caller would wake. The bridge also holds back any wake sent while the state is locked until the lock is released. UniFFI runs the foreign continuation on the waking thread, so a binding may poll the woken call right there, and it must not find the state still locked.cancel()closes the channel, then drops the state before it returns, inside the runtime. A panic during that drop is reported by later calls instead of unwinding into the caller. Concurrent calls on one handle all park, and each poll takes the next item atomically.read_frameon a track runs its whole step in one poll: acquire the next group ifpendingis empty, then read its first frame. If another call took the group between polls, the next poll acquires a new one. A group still waiting on its first frame stays inpending, so a cancelledread_framestill leaves it fornext_group. Whennext_grouptakes a group out ofpending, it wakes the bridge, so aread_frameparked on that group moves on.Shutdown's in-flight count is now an atomic with a stop bit. Before, it took a global mutex twice per poll, on the
Taskpath as well. A condvar is used only for the last poll that shutdown waits for.Inventory
MoqTrackConsumer::{recv_group, next_group, read_frame, recv_datagram}ReadLanetasks are goneMoqGroupConsumer::read_framepoll_read_frameMoqAnnounceConsumer::nextpoll_nextMoqFollowing::availablepoll_availableMoqOriginRequests::requested_broadcastpoll_requested_broadcast; the shared slot is goneMoqJsonSnapshotConsumer::{next, latest},MoqJsonStreamConsumer::next,MoqJsonWindowConsumer::nextpoll_*MoqMediaCatalogConsumer::next,MoqMediaTrackConsumer::next,MoqMediaGroupConsumer::nextpoll_*; container parsing only, no codecMoqBroadcastRequests::requested_track,MoqTrackRequests::requested_fill,MoqFill::wanted_changedpoll_*MoqGrantConsumer::changedWatch::poll_changedMoqBandwidthConsumer::rate_changedpoll_changed; already kio inside aTask<()>laneMoqClient::connectTaskMoqServer::{listen, accept},MoqRequest::{accept, reject}Taskconfigurerelies onBusyMoqSession::closed,MoqSession::state_changedTaskMoqVideoConsumer::next,MoqAudioConsumer::nextTaskMoqTrackDemand::wanted_changeddetachedMoqFill::unwanteddetachedMoqTokens::answereddetachedTaskMoqSession::shutdownffi::spawn)closed()waiterTask::takelost its last caller and is removed.Impact
cancel()on the migrated handles releases the state before it returns, where before a task did that later. Recorded in the moq-ffi CHANGELOG.doc/), so none change.Choices made without asking
MoqGroupConsumerhanded toMoqMediaGroupConsumer::newstill fails withBusywhile a read is in flight, counted byPolled::busy. That keeps today's behavior.MoqOriginRequests::requested_broadcastaftercancel()still returnsClosed, and a parked call still returnsCancelled, as before.read_framestep: acquire, or re-acquire when the slot is empty, then read. This is one of the options the Plan offered.TaskandPolled.Polledbridges every handle, not only the track, which is the one known to keep a single waker. The cost is that any progress on a handle wakes all of its parked calls, so a datagram can wake a parked group read. Bridging every handle keeps every handle correct without auditing each inner type's waker policy.Land ejection (2026-11-01)
The land queue ejected this PR twice with
test rsfailing. The first failure was themoq_clocktokio::clockrename, which the land fixer already handled. The second was this PR's ownraw_track_concurrent_reads_take_every_group_once, which hung in most runs on the pre-merge headd60a595f69(it failed the first of 40 stress iterations). Only one of its four readers ever woke, because moq-net's track cursor keeps one waker and each concurrent call replaced the last one's. Neither moq-dev/moq#7506 nor anything else from main caused it. Now that #7506 has landed, moq-ffi gets kio'sasyncfeature through moq-net and needs no manifest change.Fixed by bridging
Polled(above). The same change fixes CodeRabbit's finding thatnext_groupwoke parkedread_framecalls while still holding the state lock. A binding that polls inline would deadlock there, andraw_next_group_wakes_read_frame_after_unlockingtimed out before the fix.Fit with the exporter switch (2026-11-02)
On 2026-11-02 the maintainer decided that moq's bindings will switch to rust2's exporter rather than a UniFFI fork (moq-dev/moq#7648,
quest/m2/ffi-exporter.md). That decision leaves this quest in place: the same commit keptquest/m2/ffi-poll-migrate.mdand re-pointed its "no UniFFI change" link at the exporter switch.Once the switch lands, the exporter exports moq-net's own
poll_*API and moq-ffi shrinks to genuinely new API. At that pointPolledand these export bodies go away. Until then, the shipped bindings get the throughput gain and lose the read lane, so a cancelled but unfreed read no longer blocks the next one. The switch is still blocked on rust2's exporter epic and its five open children. The semantics here (no lane, concurrent reads each take the next item, a cancel ends only that read) match what the exporter's generators plan. Work outside moq-ffi survives the switch:Background::poll_failed, the atomic shutdown counter, and the tests that pin those semantics.Merge with main (2026-11-03)
Merged
origin/mainate25f6266df, no rebase. Main made frame timestamps exact (MoqTimestamp, moq-dev/moq#6946), soraw_frame,media_frame, and theMoqMediaReadconversion became infallible. The polled reads now wrap them inOk(...)instead of callingtranspose(). Main'sTask-based bodies for the same exports were dropped in favor of this PR'sPolledones. The quest deletion is kept. Main had added two links to the deleted quest in the no-spawn epic (moq-dev/moq#7519), and this merge removes them. That leavesquest/m1/poll-first/no-spawn/ffi.mdwith noRequiredentry, so it is unblocked.Validation
raw_read_frame_moves_on_when_next_group_takes_its_group: aread_frameparked on a frameless group moves on to the next group whennext_grouptakes the one it was waiting on.rust_future_*driven directly: a trackread_frameand a groupread_framethat are cancelled but not freed don't block the next read on the same handle.read_frame, twonext_group, on a multi-thread runtime) take all 200 groups exactly once.shutdown_waits_for_a_polled_call: a poll in flight when shutdown starts finishes before shutdown returns, a later call isCancelled, and a call parked across shutdown resolvesCancelled.Polledunit tests for take, busy, cancel, the cleanup panic, two concurrent calls, and two calls parked on a state that keeps one waker.raw_next_group_wakes_read_frame_after_unlocking: aread_framewhose waker polls it inline, as an unconfined coroutine would, is woken bynext_groupafter the state is unlocked.shutdown_cancels_and_drops_cleanlynow covers a parked migratedread_frame.raw_track_pending_group_read_holds_the_lane, since the lane no longer exists.just ci origin/mainpasses on head8b28e429b5(merged with main ate25f6266df): Rust, Python, Go, Kotlin, Dart, C, C++, OBS, and lint modules.quest check --base origin/mainpasses.Polledtests pass 40 of 40 runs under--stress-count 40.origin/mainat 2d13685) and head runners were staged once each, then alternated for 5 rounds at-benchtime=2s. The table shows medians. The host was shared with other agents and a single run swung up to 2x, so read these as direction, not magnitude:sequence(sync)info(sync)Head is ahead on both fan-out axes, and CPU per MB falls in every throughput case. The sync calls didn't change, so their movement shows the noise floor. The 64 KiB case fails with
evictedon base and on head alike, so it is excluded (follow-up below).Follow-ups
spike/ffi-poll-prototypebranch once this lands, as the Plan says.evictedonorigin/maintoo: one round's groups outgrow the 64 MiB origin cache budget, or the consumers fall behind its eviction.just bench-ffiwill report them against its pinned revision.Review
Reviewer: Codex, gpt-6.1-sol, medium effort (
quest review --base origin/main, a new session), head8b28e429b5058bed60000995a5758f37eaa0aa66.8b28e429b5, the merge with main): no findings.Previous session, head
3f886d3b27, after theDesign change:comment: round 1 (headafce050de0) found that the shared bridged waiter stacked duplicate registrations once a handle had more than eight parked calls. The fix gives each call its ownkio::Park. Round 2 had no findings. Before the design change, at head256438d965, aread_frameparked on a frameless pending group was not woken whennext_grouptook that group. That was fixed and is covered byraw_read_frame_moves_on_when_next_group_takes_its_group.Online review: CodeRabbit's finding on
consumer.rs(a wake sent while the state lock was held) was fixed by the bridge in3f886d3b27, and CodeRabbit confirmed it in the thread. The OpenAI review of3f886d3b27reported no findings. Pullfrog reported no issues. Its failing check is optional and comes from a billing outage, so it was ignored.(Written by Claude Opus 5.5)
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