gh-112536: Set up TSAN CI for free-threading

.github/workflows/build.yml

@@ -472,6 +472,29 @@ jobs:
     - name: Tests
       run: xvfb-run make test
 
+  build_tsan_free_threading:
+    name: 'Thread sanitizer (free-threading)'
+    runs-on: ubuntu-20.04
+    timeout-minutes: 60
+    needs: check_source
+    if: needs.check_source.outputs.run_tests == 'true'
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install Dependencies
+      run: sudo ./.github/workflows/posix-deps-apt.sh
+    - name: Set up GCC-10 for ASAN
+      uses: egor-tensin/setup-gcc@v1
+      with:
+        version: 11
+    - name: Configure CPython
+      run: ./configure --disable-gil --with-thread-sanitizer
+    - name: Build CPython
+      run: make -j4
+    - name: Display build info
+      run: make pythoninfo
+    - name: Tests
+      run: ./python -m test --pgo -j4 # Reduce test scope
+
   # CIFuzz job based on https://google.github.io/oss-fuzz/getting-started/continuous-integration/
   cifuzz:
     name: CIFuzz
@@ -561,6 +584,7 @@ jobs:
             build_windows,
             build_windows_free_threading,
             build_asan,
+            build_tsan_free_threading,
             '
             || ''
           }}

Objects/obmalloc.c

@@ -446,6 +446,7 @@ _PyMem_ArenaFree(void *Py_UNUSED(ctx), void *ptr,
 /***************************/
 
 static int
+_Py_NO_SANITIZE_THREAD
 set_default_allocator_unlocked(PyMemAllocatorDomain domain, int debug,
                                PyMemAllocatorEx *old_alloc)
 {

configure.ac

@@ -3264,6 +3264,12 @@ AC_MSG_RESULT([no])
 with_tsan="no"
 ])
 
+if test "$with_tsan" = "yes"
+then
+  AC_DEFINE([MI_TSAN], [1],
+            [Define MI_TSAN for thread sanitizer])
+fi
+
 # Set info about shared libraries.
 AC_SUBST([SHLIB_SUFFIX])
 AC_SUBST([LDSHARED])

pyconfig.h.in

@@ -1588,6 +1588,9 @@
    <sysmacros.h>. */
 #undef MAJOR_IN_SYSMACROS
 
+/* Define MI_TSAN for thread sanitizer */
+#undef MI_TSAN
+
 /* Define if mvwdelch in curses.h is an expression. */
 #undef MVWDELCH_IS_EXPRESSION