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Fix dict concurrency stability #7231

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Merged
youknowone merged 1 commit into from
Feb 27, 2026
Merged

Fix dict concurrency stability #7231

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83 changes: 46 additions & 37 deletions crates/vm/src/dict_inner.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -292,7 +292,11 @@ impl<T: Clone> Dict<T> {
// The dict was changed since we did lookup. Let's try again.
}
} else {
// New key:
// New key - validate slot is still what lookup found
if inner.indices.get(index_index) != Some(&entry_index) {
// Dict was resized since lookup, retry
continue;
}
inner.unchecked_push(index_index, hash, key.to_pyobject(vm), value, entry_index);
break None;
}
Expand Down Expand Up @@ -431,6 +435,9 @@ impl<T: Clone> Dict<T> {
}
} else {
let mut inner = self.write();
if inner.indices.get(index_index) != Some(&entry) {
continue;
}
inner.unchecked_push(index_index, hash, key.to_owned(), value, entry);
break None;
}
Expand All @@ -444,31 +451,32 @@ impl<T: Clone> Dict<T> {
F: FnOnce() -> T,
{
let hash = key.key_hash(vm)?;
let res = loop {
let lookup = self.lookup(vm, key, hash, None)?;
let (index_entry, index_index) = lookup;
let mut default = Some(default);
loop {
let (index_entry, index_index) = self.lookup(vm, key, hash, None)?;
if let Some(index) = index_entry.index() {
let inner = self.read();
if let Some(entry) = inner.get_entry_checked(index, index_index) {
break entry.value.clone();
} else {
// The dict was changed since we did lookup, let's try again.
continue;
return Ok(entry.value.clone());
}
} else {
let value = default();
let mut inner = self.write();
inner.unchecked_push(
index_index,
hash,
key.to_pyobject(vm),
value.clone(),
index_entry,
);
break value;
continue;
}
};
Ok(res)
let mut inner = self.write();
if inner.indices.get(index_index) != Some(&index_entry) {
continue;
}
let value = default
.take()
.expect("default must only be computed on insertion")();
inner.unchecked_push(
index_index,
hash,
key.to_pyobject(vm),
value.clone(),
index_entry,
);
return Ok(value);
}
}

#[allow(dead_code)]
Expand All @@ -483,27 +491,28 @@ impl<T: Clone> Dict<T> {
F: FnOnce() -> T,
{
let hash = key.key_hash(vm)?;
let res = loop {
let lookup = self.lookup(vm, key, hash, None)?;
let (index_entry, index_index) = lookup;
let mut default = Some(default);
loop {
let (index_entry, index_index) = self.lookup(vm, key, hash, None)?;
if let Some(index) = index_entry.index() {
let inner = self.read();
if let Some(entry) = inner.get_entry_checked(index, index_index) {
break (entry.key.clone(), entry.value.clone());
} else {
// The dict was changed since we did lookup, let's try again.
continue;
return Ok((entry.key.clone(), entry.value.clone()));
}
} else {
let value = default();
let key = key.to_pyobject(vm);
let mut inner = self.write();
let ret = (key.clone(), value.clone());
inner.unchecked_push(index_index, hash, key, value, index_entry);
break ret;
continue;
}
};
Ok(res)
let mut inner = self.write();
if inner.indices.get(index_index) != Some(&index_entry) {
continue;
}
let value = default
.take()
.expect("default must only be computed on insertion")();
let key_obj = key.to_pyobject(vm);
let ret = (key_obj.clone(), value.clone());
inner.unchecked_push(index_index, hash, key_obj, value, index_entry);
return Ok(ret);
}
}

pub fn len(&self) -> usize {
Expand Down
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