Adds `scheduler::spawn_dedicated_thread` (and inherent `spawn_dedicated`
methods on `PlatformScheduler` and `TestScheduler`) so single-threaded
actors that own `!Send` state can run on their own OS thread and freely
do blocking I/O without disturbing any other executor.
### Why
A single-threaded actor that needs to do blocking syscalls is currently
stuck: it can't run on the shared foreground executor (blocking would
stall every other foreground session), and it can't move to the
background pool because its state isn't `Send`. `spawn_dedicated` gives
each such actor its own thread and its own `LocalExecutor`, while still
participating in the same testable scheduler infrastructure as
everything else.
### Shape
- `pub fn spawn_dedicated_thread(session_id, scheduler, f) -> Task<_>`
in `scheduler`. Owns the OS thread, the per-session runnable channel,
and the `LocalExecutor` setup.
- Inherent `spawn_dedicated` on `PlatformScheduler` (allocates its own
`SessionId`, delegates to the free function).
- Inherent `spawn_dedicated` on `TestScheduler` (no real thread — runs
as a fresh local session driven by the test scheduler's run loop, so
determinism under `many` is preserved).
- Renames `Scheduler::schedule_foreground` → `schedule_local` and
`scheduler::ForegroundExecutor` → `scheduler::LocalExecutor` to reflect
that these are session-pinned queues rather than "the main thread" (a
dedicated session runs on its own thread). GPUI's wrapper
`gpui::ForegroundExecutor` and the `foreground_executor` field/method
names are unchanged to keep blast radius small.
- `LocalExecutor::new` now takes an explicit dispatch closure, so the
routing decision (default session, dedicated thread, or something else)
lives at the construction site.
### Tests
- `TestScheduler` side: round-trip, `!Send` future, `Send` closure
capturing shared state, inner `executor.spawn`, determinism under `many`
seeds, drop-cancels-future, detached child runs after root completes.
- `PlatformScheduler` side: real separate thread (blocking syscalls
don't stall the test), `!Send` future output, drop-cancels-future,
thread tears down after work completes, detached child outlives root.
cc @as-cii
Release Notes:
- N/A
---------
Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
async_tasks can build a cycle with the scheduler where the runnable
itself keeps a reference to the scheduler and the scheduler keeping
references to the runnable. This effectively can cause scheduler / task
leaks, most notably in test environments, so we break this cycle by
using weak pointers instead.
Release Notes:
- N/A or Added/Fixed/Improved ...
Co-Authored-By: Eric Holk <eric@zed.dev>
In app drop we had been calling `.close()` on the executors. This caused
problems with the BackgroundExecutor on Linux because it raced with
concurrent work: If task A was running and about to poll task B, the
poll to task B would panic with "Task polled after completion". This
didn't really matter (because the app was shutting down anyway) but
inflated our panic metrics on Linux.
It turns out that the call to `.close()` is not needed. It was added to
prevent foreground tasks being scheduled after the app was dropped; but
on all platforms the App run method does not return until after the
ForegroundExecutor is stopped (so no further tasks will run anyway).
The background case is more interesting. In test code it didn't matter
(the background executor is simulated on the main thread so tests can't
leak tasks); in app code it also didn't really make a difference. When
`fn main` returns (which it does immediately after the app is dropped)
all the background threads will be cancelled anyway.
Further confounding debugging, it turns out that the App does not get
dropped on macOS and Windows due to a reference cycle; so this was only
happening on Linux where the app quit callback is dropped instead of
retained after being called. (Fix in #50985)
Release Notes:
- N/A
---------
Co-authored-by: Eric Holk <eric@zed.dev>
This does not yet allow for finding task <-> entity cycles
unfortunately, but at least it does catch entity <-> entity cycles for
the time being
Release Notes:
- N/A *or* Added/Fixed/Improved ...
Implements a basic web platform for the wasm32-unknown-unknown target
for gpui
Release Notes:
- N/A *or* Added/Fixed/Improved ...
---------
Co-authored-by: John Tur <john-tur@outlook.com>
The scheduler integration (#44810) removed the special handling for
realtime audio tasks that spawn them on a dedicated thread. This caused
a panic in the Mac dispatcher when RealtimeAudio priority was passed to
the regular dispatch path.
This restores the original behavior: RealtimeAudio tasks are spawned on
a dedicated thread via dispatcher.spawn_realtime(), using a bounded
channel to send runnables to it.
Release Notes:
- N/A
## Motivation
This PR unifies the async execution infrastructure between GPUI and
other components that depend on the `scheduler` crate (such as our cloud
codebase). By having a scheduler that lives independently of GPUI, we
can enable deterministic testing across the entire stack - testing GPUI
applications alongside cloud services with a single, unified scheduler.
## Summary
This PR completes the integration of the `scheduler` crate into GPUI,
unifying async execution and enabling deterministic testing of GPUI
combined with other components that depend on the scheduler crate.
## Key Changes
### Scheduler Integration (Phases 1-5, previously completed)
- `TestDispatcher` now delegates to `TestScheduler` for timing, clock,
RNG, and task scheduling
- `PlatformScheduler` implements the `Scheduler` trait for production
use
- GPUI executors wrap scheduler executors, selecting `TestScheduler` or
`PlatformScheduler` based on environment
- Unified blocking logic via `Scheduler::block()`
### Dead Code Cleanup
- Deleted orphaned `crates/gpui/src/platform/platform_scheduler.rs`
(older incompatible version)
## Intentional Removals
### `spawn_labeled` and `deprioritize` removed
The `TaskLabel` system (`spawn_labeled`, `deprioritize`) was removed
during this integration. It was only used in a few places for test
ordering control.
cc @maxbrunsfeld @as-cii - The new priority-weighted scheduling in
`TestScheduler` provides similar functionality through
`Priority::High/Medium/Low`. If `deprioritize` is important for specific
test scenarios, we could add it back to the scheduler crate. Let me know
if this is blocking anything.
### `start_waiting` / `finish_waiting` debug methods removed
Replaced by `TracingWaker` in `TestScheduler` - run tests with
`PENDING_TRACES=1` to see backtraces of pending futures when parking is
forbidden.
### Realtime Priority removed
The realtime priority feature was unused in the codebase. I'd prefer to
reintroduce it when we have an actual use case, as the implementation
(bounded channel with capacity 1) could potentially block the main
thread. Having a real use case will help us validate the design.
## Testing
- All GPUI tests pass
- All scheduler tests pass
- Clippy clean
## Architecture
```
┌─────────────────────────────────────────────────────────────┐
│ GPUI │
│ ┌──────────────────────┐ ┌────────────────────────────┐ │
│ │ gpui::Background- │ │ gpui::ForegroundExecutor │ │
│ │ Executor │ │ - wraps scheduler:: │ │
│ │ - scheduler: Arc< │ │ ForegroundExecutor │ │
│ │ dyn Scheduler> │ └────────────┬───────────────┘ │
│ └──────────┬───────────┘ │ │
│ │ │ │
│ └──────────┬──────────────────┘ │
│ ▼ │
│ ┌───────────────────────┐ │
│ │ Arc<dyn Scheduler> │ │
│ └───────────┬───────────┘ │
│ ┌──────────────┴──────────────┐ │
│ ▼ ▼ │
│ ┌──────────────────┐ ┌────────────────────┐ │
│ │ PlatformScheduler│ │ TestScheduler │ │
│ │ (production) │ │ (deterministic) │ │
│ └──────────────────┘ └────────────────────┘ │
└─────────────────────────────────────────────────────────────┘
```
Release Notes:
- N/A
---------
Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Yara <git@yara.blue>
Co-authored-by: Zed Zippy <234243425+zed-zippy[bot]@users.noreply.github.com>
Extracts and cleans up GPUI's scheduler code into a new `scheduler`
crate, making it pluggable by external runtimes. This will enable
deterministic integration testing with cloud components by providing a
unified test scheduler across Zed and backend code. In Zed, it will
replace the existing GPUI scheduler for consistent async task management
across platforms.
## Changes
- **Core Implementation**: `TestScheduler` with seed-based
randomization, session tracking (`SessionId`), and foreground/background
task separation for reproducible testing.
- **Executors**: `ForegroundExecutor` (!Send, thread-local) and
`BackgroundExecutor` (Send, with blocking/timeout support) as
GPUI-compatible wrappers.
- **Clock and Timer**: Controllable `TestClock` and future-based `Timer`
for time-sensitive tests.
- **Testing APIs**: `once()`, `with_seed()`, and `many()` methods for
configurable test runs.
- **Dependencies**: Added `async-task`, `chrono`, `futures`, etc., with
updates to `Cargo.toml` and lock file.
## Benefits
- **Integration Testing**: Facilitates reliable async tests involving
cloud sessions, reducing flakiness via deterministic execution.
- **Pluggability**: Trait-based design (`Scheduler`) allows easy
integration into non-GPUI runtimes while maintaining GPUI compatibility.
- **Cleanup**: Refactors GPUI scheduler logic for clarity, correctness
(no `unwrap()`, proper error handling), and extensibility.
Follows Rust guidelines; run `./script/clippy` for verification.
- [x] Define and test a core scheduler that we think can power our cloud
code and GPUI
- [ ] Replace GPUI's scheduler
Release Notes:
- N/A
---------
Co-authored-by: Antonio Scandurra <me@as-cii.com>
