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Fix parking lot hash table after fork #6963

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Fix parking lot hash table after fork #6963

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4 changes: 2 additions & 2 deletions Cargo.lock
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3 changes: 3 additions & 0 deletions Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,8 @@ lto = "thin"
[patch.crates-io]
# REDOX START, Uncomment when you want to compile/check with redoxer
# REDOX END
# Fork-safety: expose reinit_after_fork() to reset global hash table after fork
parking_lot_core = { git = "https://github.com/youknowone/parking_lot", rev = "5953f33ea399365bd15fdd9b6aaf8bc5ad7c8e46" }

[package.metadata.packager]
product-name = "RustPython"
Expand Down Expand Up @@ -184,6 +186,7 @@ num_enum = { version = "0.7", default-features = false }
optional = "0.5"
once_cell = "1.20.3"
parking_lot = "0.12.3"
parking_lot_core = { version = "0.9.12" }
paste = "1.0.15"
proc-macro2 = "1.0.105"
pymath = { version = "0.1.5", features = ["mul_add", "malachite-bigint", "complex"] }
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1 change: 1 addition & 0 deletions crates/vm/Cargo.toml
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Expand Up @@ -93,6 +93,7 @@ unic-ucd-category = { workspace = true }
unic-ucd-ident = { workspace = true }

[target.'cfg(unix)'.dependencies]
parking_lot_core = { workspace = true, features = ["fork"] }
rustix = { workspace = true }
nix = { workspace = true }
exitcode = "1.1.2"
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20 changes: 6 additions & 14 deletions crates/vm/src/stdlib/thread.rs
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Expand Up @@ -147,15 +147,9 @@ pub(crate) mod _thread {

#[pymethod]
fn _at_fork_reinit(&self, _vm: &VirtualMachine) -> PyResult<()> {
if self.mu.is_locked() {
unsafe {
self.mu.unlock();
};
}
// Casting to AtomicCell is as unsafe as CPython code.
// Using AtomicCell will prevent compiler optimizer move it to somewhere later unsafe place.
// It will be not under the cell anymore after init call.

// Don't call unlock() — it may invoke unlock_slow() which accesses
// parking_lot_core's global hash table that is stale after fork().
// Just overwrite the mutex with a fresh INIT value.
let new_mut = RawMutex::INIT;
unsafe {
let old_mutex: &AtomicCell<RawMutex> = core::mem::transmute(&self.mu);
Expand Down Expand Up @@ -247,11 +241,9 @@ pub(crate) mod _thread {

#[pymethod]
fn _at_fork_reinit(&self, _vm: &VirtualMachine) -> PyResult<()> {
if self.mu.is_locked() {
unsafe {
self.mu.unlock();
};
}
// Don't call unlock() — it may invoke unlock_slow() which accesses
// parking_lot_core's global hash table that is stale after fork().
// Just overwrite the mutex with a fresh INIT value.
self.count.store(0, core::sync::atomic::Ordering::Relaxed);
let new_mut = RawRMutex::INIT;
unsafe {
Expand Down
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