From 8c1a6237d2b0e869e717b153078c7b6cc86cb216 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Tue, 16 Jun 2026 14:28:43 +0200
Subject: [PATCH] gh-151542: Use at least 2 MiB stack size, instead of 1 MiB

Python needs at least 2 MiB stack to run test_threading on Free
Threading.
---
 .../Build/2026-06-16-14-30-41.gh-issue-151542.QrLE0K.rst | 3 +++
 configure                                                | 4 ++--
 configure.ac                                             | 9 +++++----
 3 files changed, 10 insertions(+), 6 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Build/2026-06-16-14-30-41.gh-issue-151542.QrLE0K.rst

diff --git a/Misc/NEWS.d/next/Build/2026-06-16-14-30-41.gh-issue-151542.QrLE0K.rst b/Misc/NEWS.d/next/Build/2026-06-16-14-30-41.gh-issue-151542.QrLE0K.rst
new file mode 100644
index 000000000000000..ee17827fd526b2f
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2026-06-16-14-30-41.gh-issue-151542.QrLE0K.rst
@@ -0,0 +1,3 @@
+Python now uses a stack size of at least 2 MiB, instead of 1 MiB. This is
+especially needed when Python is linked to musl (ex: Alpine Linux) which
+uses a default stack of 128 kiB. Patch by Victor Stinner.
diff --git a/configure b/configure
index 7608a0493b0ee62..1ebb5f8bbceb3ef 100755
--- a/configure
+++ b/configure
@@ -9901,7 +9901,7 @@ int main()
         return 2;
     }
 
-    if (size < 1024 * 1024) {
+    if (size < 2 * 1024 * 1024) {
         return 1;
     }
     return 0;
@@ -9913,7 +9913,7 @@ EOF
         ./conftest &>/dev/null
         exitcode=$?
         if test $exitcode -eq 1; then
-            ac_cv_thread_stack_size=1048576
+            ac_cv_thread_stack_size=2097152  # 2 MiB
         elif test $exitcode -eq 0; then
             ac_cv_thread_stack_size="default"
         fi
diff --git a/configure.ac b/configure.ac
index 020861b4c823759..1539e156a10413d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2463,8 +2463,9 @@ AS_CASE([$ac_sys_system],
 )
 
 dnl On Linux, check the thread stack size. musl (ex: Alpine Linux) uses
-dnl a default thread stack size of 128 kB, whereas the glibc uses 8 MiB.
-dnl Python needs at least 1 MiB.
+dnl a default thread stack size of 128 kiB, whereas the glibc uses 8 MiB.
+dnl Python needs at least 2 MiB to run test_threading on Free Threading
+dnl (gh-151542).
 if test "$ac_sys_system" = "Linux" -a "$cross_compiling" = no; then
     AC_CACHE_CHECK([for thread stack size], [ac_cv_thread_stack_size], [
     cat > conftest.c <<EOF
@@ -2485,7 +2486,7 @@ int main()
         return 2;
     }
 
-    if (size < 1024 * 1024) {
+    if (size < 2 * 1024 * 1024) {
         return 1;
     }
     return 0;
@@ -2497,7 +2498,7 @@ EOF
         ./conftest &>/dev/null
         exitcode=$?
         if test $exitcode -eq 1; then
-            ac_cv_thread_stack_size=1048576
+            ac_cv_thread_stack_size=2097152  # 2 MiB
         elif test $exitcode -eq 0; then
             ac_cv_thread_stack_size="default"
         fi