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Revert "fix(wasm): never swap to a fiber while an Asyncify context is parked"

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This reverts commit 32218122c3.
This commit is contained in:
Gergő Törcsvári 2026-07-29 17:29:28 +02:00
commit 64d2cdf259
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1 changed files with 0 additions and 42 deletions
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42
wasm/bindings/collab_common.h
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@ -61,36 +61,6 @@ inline bool& fiberBusy()
return busy; return busy;
} }
/**
* True while an Asyncify unwind/rewind or park is IN FLIGHT (the single
* `currData` slot is taken by somebody else's suspended context).
*
* Starting a fiber in that window is the documented crash family
* (docs/features/async/13, "scheduler invariant"): `emscripten_fiber_swap`
* calls `stop_unwind`, which asserts/corrupts when another context is parked —
* surfacing as "index out of bounds", "unreachable executed" or "indirect call
* signature mismatch", after which the runtime is poisoned and every later
* event traps.
*
* Normally the slot is FREE here: the main loop's per-frame
* `wxWasmYieldToBrowser` completes every frame, so `drainFibers` (a
* CallAfter, drained from ProcessEvents) runs between yields with nothing in
* flight. It is NOT free when a nested/modal pump tick drives ProcessEvents
* while the chain that opened the modal is parked deeper down the stack —
* exactly what a big board open does (progress dialog over a parked load),
* and the window in which a presence/collab body arriving off the WebSocket
* used to swap a fiber and take the runtime down.
*
* The wx dispatch interlock (wx/wasm/private/dispatch.h) does not cover this:
* the modal parks deliberately zero its count so their own pump may dispatch.
*/
inline bool asyncifyInFlight()
{
return EM_ASM_INT( {
return ( typeof Asyncify !== "undefined" && Asyncify.currData ) ? 1 : 0;
} ) != 0;
}
/* The in-flight body. HEAP-allocated and pinned for the body's whole life: /* The in-flight body. HEAP-allocated and pinned for the body's whole life:
* when a body PARKS (asyncify suspension inside commit.Push), COROUTINE::Call * when a body PARKS (asyncify suspension inside commit.Push), COROUTINE::Call
* RETURNS EARLY — the later asyncify rewind re-enters the fiber through the * RETURNS EARLY — the later asyncify rewind re-enters the fiber through the
@ -148,18 +118,6 @@ inline void drainFibers()
while( !q.empty() ) while( !q.empty() )
{ {
// Someone else's context is parked in the single Asyncify slot: swapping
// to a fiber now corrupts it (see asyncifyInFlight). Re-queue and retry
// on the next drained tick — bodies are viewport/overlay/apply work, so
// waiting out the park costs latency, never correctness.
if( asyncifyInFlight() )
{
if( wxEvtHandler* h = fiberHandler() )
h->CallAfter( []() { drainFibers(); } );
return;
}
fiberBusy() = true; fiberBusy() = true;
slot.done = false; slot.done = false;
slot.body = new std::function<void()>( std::move( q.front() ) ); slot.body = new std::function<void()>( std::move( q.front() ) );