From 0e202dfd192946245e5021b938517aa35145ba9c Mon Sep 17 00:00:00 2001
From: Nathan Goldbaum <nathan.goldbaum@gmail.com>
Date: Mon, 24 Mar 2025 09:41:40 -0600
Subject: [PATCH] BUG: avoid deadlocks with C++ shared mutex in dispatch cache

---
 numpy/_core/src/umath/dispatching.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/numpy/_core/src/umath/dispatching.cpp b/numpy/_core/src/umath/dispatching.cpp
index d33899b4257b..ba98a9b5c5d1 100644
--- a/numpy/_core/src/umath/dispatching.cpp
+++ b/numpy/_core/src/umath/dispatching.cpp
@@ -912,7 +912,9 @@ promote_and_get_info_and_ufuncimpl_with_locking(
         npy_bool legacy_promotion_is_possible)
 {
     std::shared_mutex *mutex = ((std::shared_mutex *)((PyArrayIdentityHash *)ufunc->_dispatch_cache)->mutex);
+    NPY_BEGIN_ALLOW_THREADS
     mutex->lock_shared();
+    NPY_END_ALLOW_THREADS
     PyObject *info = PyArrayIdentityHash_GetItem(
             (PyArrayIdentityHash *)ufunc->_dispatch_cache,
             (PyObject **)op_dtypes);
@@ -926,7 +928,9 @@ promote_and_get_info_and_ufuncimpl_with_locking(
 
     // cache miss, need to acquire a write lock and recursively calculate the
     // correct dispatch resolution
+    NPY_BEGIN_ALLOW_THREADS
     mutex->lock();
+    NPY_END_ALLOW_THREADS
     info = promote_and_get_info_and_ufuncimpl(ufunc,
             ops, signature, op_dtypes, legacy_promotion_is_possible);
     mutex->unlock();