bpo-40521: Make context free list per-interpreter (GH-20644)

Each interpreter now has its own context free list:

* Move context free list into PyInterpreterState.
* Add _Py_context_state structure.
* Add tstate parameter to _PyContext_ClearFreeList()
  and _PyContext_Fini().
* Pass tstate to clear_freelists().

1 files changed, 19 insertions, 16 deletions

diff --git a/Python/context.c b/Python/context.c
index bacc701..3cf8db4 100644
--- a/Python/context.c
+++ b/Python/context.c
@@ -10,8 +10,6 @@
 
 
 #define CONTEXT_FREELIST_MAXLEN 255
-static PyContext *ctx_freelist = NULL;
-static int ctx_freelist_len = 0;
 
 
 #include "clinic/context.c.h"
@@ -334,11 +332,13 @@ class _contextvars.Context "PyContext *" "&PyContext_Type"
 static inline PyContext *
 _context_alloc(void)
 {
+    PyInterpreterState *interp = _PyInterpreterState_GET();
+    struct _Py_context_state *state = &interp->context;
     PyContext *ctx;
-    if (ctx_freelist_len) {
-        ctx_freelist_len--;
-        ctx = ctx_freelist;
-        ctx_freelist = (PyContext *)ctx->ctx_weakreflist;
+    if (state->numfree) {
+        state->numfree--;
+        ctx = state->freelist;
+        state->freelist = (PyContext *)ctx->ctx_weakreflist;
         ctx->ctx_weakreflist = NULL;
         _Py_NewReference((PyObject *)ctx);
     }
@@ -458,10 +458,12 @@ context_tp_dealloc(PyContext *self)
     }
     (void)context_tp_clear(self);
 
-    if (ctx_freelist_len < CONTEXT_FREELIST_MAXLEN) {
-        ctx_freelist_len++;
-        self->ctx_weakreflist = (PyObject *)ctx_freelist;
-        ctx_freelist = self;
+    PyInterpreterState *interp = _PyInterpreterState_GET();
+    struct _Py_context_state *state = &interp->context;
+    if (state->numfree < CONTEXT_FREELIST_MAXLEN) {
+        state->numfree++;
+        self->ctx_weakreflist = (PyObject *)state->freelist;
+        state->freelist = self;
     }
     else {
         Py_TYPE(self)->tp_free(self);
@@ -1271,11 +1273,12 @@ get_token_missing(void)
 
 
 void
-_PyContext_ClearFreeList(void)
+_PyContext_ClearFreeList(PyThreadState *tstate)
 {
-    for (; ctx_freelist_len; ctx_freelist_len--) {
-        PyContext *ctx = ctx_freelist;
-        ctx_freelist = (PyContext *)ctx->ctx_weakreflist;
+    struct _Py_context_state *state = &tstate->interp->context;
+    for (; state->numfree; state->numfree--) {
+        PyContext *ctx = state->freelist;
+        state->freelist = (PyContext *)ctx->ctx_weakreflist;
         ctx->ctx_weakreflist = NULL;
         PyObject_GC_Del(ctx);
     }
@@ -1283,10 +1286,10 @@ _PyContext_ClearFreeList(void)
 
 
 void
-_PyContext_Fini(void)
+_PyContext_Fini(PyThreadState *tstate)
 {
     Py_CLEAR(_token_missing);
-    _PyContext_ClearFreeList();
+    _PyContext_ClearFreeList(tstate);
     _PyHamt_Fini();
 }