Replace PyFunction.code PyMutex with PyAtomicRef for lock-free reads#7317
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youknowone merged 1 commit intoRustPython:mainfrom Mar 3, 2026
Merged
Replace PyFunction.code PyMutex with PyAtomicRef for lock-free reads#7317youknowone merged 1 commit intoRustPython:mainfrom
youknowone merged 1 commit intoRustPython:mainfrom
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Change the code field from PyMutex<PyRef<PyCode>> to PyAtomicRef<PyCode>, eliminating mutex lock/unlock on every function call. The setter uses swap_to_temporary_refs for safe deferred drop of the old code object.
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📝 WalkthroughWalkthroughThe pull request refactors PyFunction's code field from a mutex-protected reference to an atomic reference, eliminating lock-based access patterns across getters, setters, and JIT paths while maintaining thread-safe semantics. Changes
Estimated code review effort🎯 3 (Moderate) | ⏱️ ~20 minutes Possibly related PRs
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Actionable comments posted: 1
🤖 Prompt for all review comments with AI agents
Verify each finding against the current code and only fix it if needed.
Inline comments:
In `@crates/vm/src/builtins/function.rs`:
- Around line 682-684: When assigning a new code object in set___code__, also
invalidate any cached JIT artifacts so the old machine code cannot be used;
specifically, after self.code.swap_to_temporary_refs(...) and before/after
self.func_version.store(0, Relaxed), clear the cached jitted_code (and any
associated owner/version fields used by the JIT fast path) so invoke_with_locals
cannot find/execute stale compiled code — update the fields that hold the
compiled entry (jitted_code) to a neutral/empty state consistent with how they
are checked in invoke_with_locals.
Comment on lines
+682
to
684
| fn set___code__(&self, code: PyRef<PyCode>, vm: &VirtualMachine) { | ||
| self.code.swap_to_temporary_refs(code, vm); | ||
| self.func_version.store(0, Relaxed); |
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Invalidate cached JIT code when __code__ is reassigned.
Line 683 swaps the code object, but the cached jitted_code is not reset. The JIT fast path in invoke_with_locals (Line 533 onward) still executes cached compiled code when present, so f.__code__ = ... can leave the function running stale machine code.
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.
In `@crates/vm/src/builtins/function.rs` around lines 682 - 684, When assigning a
new code object in set___code__, also invalidate any cached JIT artifacts so the
old machine code cannot be used; specifically, after
self.code.swap_to_temporary_refs(...) and before/after
self.func_version.store(0, Relaxed), clear the cached jitted_code (and any
associated owner/version fields used by the JIT fast path) so invoke_with_locals
cannot find/execute stale compiled code — update the fields that hold the
compiled entry (jitted_code) to a neutral/empty state consistent with how they
are checked in invoke_with_locals.
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Change the code field from PyMutex<PyRef> to PyAtomicRef, eliminating mutex lock/unlock on every function call. The setter uses swap_to_temporary_refs for safe deferred drop of the old code object.
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