[Mlir-commits] [mlir] [mlir][python] Cache import of ir module in type casters. (PR #160000)

[Oleksandr Alex Zinenko]

================
@@ -30,6 +32,57 @@
 // clang-format on
 #include "llvm/ADT/Twine.h"
 
+namespace mlir {
+namespace python {
+namespace {
+
+// Safely calls Python initialization code on first use, avoiding deadlocks.
+template <typename T>
+class SafeInit {
+public:
+  typedef std::unique_ptr<T> (*F)();
+
+  explicit SafeInit(F init_fn) : init_fn_(init_fn) {}
+
+  T &Get() {
+    if (T *result = output_.load()) {
+      return *result;
+    }
+
+    // Note: init_fn() may be called multiple times if, for example, the GIL is
+    // released during its execution. The intended use case is for module
+    // imports which are safe to perform multiple times. We are careful not to
+    // hold a lock across init_fn() to avoid lock ordering problems.
+    std::unique_ptr<T> m = init_fn_();
+    {
+      nanobind::ft_lock_guard lock(mu_);
+      if (T *result = output_.load()) {
+        return *result;
+      }
+      T *p = m.release();
+      output_.store(p);
+      return *p;
+    }
+  }
+
+private:
+  nanobind::ft_mutex mu_;
+  std::atomic<T *> output_{nullptr};
+  F init_fn_;
----------------
ftynse wrote:

```suggestion
  nanobind::ft_mutex mu;
  std::atomic<T *> output{nullptr};
  F initFn;
```

Nit: LLVM naming convention

https://github.com/llvm/llvm-project/pull/160000