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EBR based GC #6849

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EBR based GC #6849

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f28ea16
Fix GC weakref clearing order
youknowone Jun 26, 2026
574e86a
Run CDPT in cooperative collection mode
youknowone Jul 1, 2026
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Run CDPT in cooperative collection mode 
Select CDPT's cooperative collection mode before the collection guard's
first pin, so CDPT never deploys a background collector thread. The
guard is only a barrier; a background thread would make the process
multi-threaded, breaking fork and signal semantics and burning CPU
while idle.

Pin CDPT to a git revision that provides the selectable collection mode.

Assisted-by: Claude
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@youknowone
youknowone committed Jul 3, 2026
commit 574e86a54b7c189a24ddc3d6bc950391cd92f1a1
16 changes: 7 additions & 9 deletions Cargo.lock
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2 changes: 1 addition & 1 deletion Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -201,7 +201,7 @@ bitflagset = "0.0.3"
bstr = "1"
bzip2 = "0.6"
chrono = { version = "0.4.44", default-features = false, features = ["clock", "std"] }
cdpt = "0.1.0"
cdpt = { git = "https://github.com/youknowone/cdpt", rev = "125a2a4c6c5ed3ba4f2550eeb8a3d44b71716a80" }
console_error_panic_hook = "0.1"
constant_time_eq = "0.5"
cranelift = "0.132.0"
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16 changes: 14 additions & 2 deletions crates/vm/src/gc_state.rs
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Expand Up @@ -414,9 +414,21 @@ impl GcState {
};

// Keep a CDPT guard during collection, following origin/gc's
// coarse-grained guarded collection experiment.
// coarse-grained guarded collection experiment. Run CDPT in cooperative
// mode so it never spawns a background collector thread: the guard here
// is only a barrier, and a background thread would make the process
// multi-threaded (breaking fork/signal semantics) and burn CPU while
// idle. Selecting the mode before this first `pin()` keeps the thread
// from being deployed at all.
#[cfg(not(target_arch = "wasm32"))]
let _cdpt_guard = cdpt::pin();
let _cdpt_guard = {
// This is the only `cdpt::pin()` in the process, and the mode is
// selected right before it, so cooperative mode always latches and
// no background collector thread is ever deployed.
let cooperative = cdpt::global().set_collection_mode(cdpt::CollectionMode::Cooperative);
debug_assert!(cooperative, "CDPT must run in cooperative mode");
cdpt::pin()
};

// Memory barrier to ensure visibility of all reference count updates
// from other threads before we start analyzing the object graph.
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