Backout changeset 46393019b650

test_capi is failing and the fix is not trivial, I prefer to revert

Doc/whatsnew/3.4.rst

@@ -1068,8 +1068,3 @@ that may require changes to your code.
   working directory will also now have an absolute path, including when using
   ``-m`` with the interpreter (this does not influence when the path to a file
   is specified on the command-line).
-
-* (C API) :c:func:`PyThread_set_key_value` now always set the value. In Python
-  3.3, the function did nothing if the key already exists (if the current
-  value is a non-NULL pointer).
-

Misc/NEWS

@@ -10,10 +10,6 @@ Release date: 2014-01-05
 Core and Builtins
 -----------------
 
-- Issue #19787: PyThread_set_key_value() now always set the value. In Python
-  3.3, the function did nothing if the key already exists (if the current value
-  is a non-NULL pointer).
-
 - Issue #14432: Remove the thread state field from the frame structure. Fix a
   crash when a generator is created in a C thread that is destroyed while the
   generator is still used. The issue was that a generator contains a frame, and

Modules/_testcapimodule.c

@@ -2511,10 +2511,6 @@ run_in_subinterp(PyObject *self, PyObject *args)
     r = PyRun_SimpleString(code);
     Py_EndInterpreter(substate);
 
-    /* restore previous thread safe. It was replaced by Py_NewInterpreter()
-       which creates a new thread state. */
-    _PyThreadState_Init(mainstate);
-
     PyThreadState_Swap(mainstate);
 
     return PyLong_FromLong(r);

Modules/_tracemalloc.c

@@ -168,11 +168,14 @@ set_reentrant(int reentrant)
     assert(reentrant == 0 || reentrant == 1);
     if (reentrant) {
         assert(PyThread_get_key_value(tracemalloc_reentrant_key) == NULL);
-        PyThread_set_key_value(tracemalloc_reentrant_key, REENTRANT);
+        PyThread_set_key_value(tracemalloc_reentrant_key,
+                               REENTRANT);
     }
     else {
-        assert(PyThread_get_key_value(tracemalloc_reentrant_key) == REENTRANT);
+        /* FIXME: PyThread_set_key_value() cannot be used to set the flag
-        PyThread_set_key_value(tracemalloc_reentrant_key, NULL);
+           to zero, because it does nothing if the variable has already
+           a value set. */
+        PyThread_delete_key_value(tracemalloc_reentrant_key);
     }
 }
 

Python/thread.c

@@ -205,7 +205,7 @@ static int nkeys = 0;  /* PyThread_create_key() hands out nkeys+1 next */
  * segfaults.  Now we lock the whole routine.
  */
 static struct key *
-find_key(int key, int update, void *value)
+find_key(int key, void *value)
 {
     struct key *p, *prev_p;
     long id = PyThread_get_thread_ident();
@@ -215,11 +215,8 @@ find_key(int key, int update, void *value)
     PyThread_acquire_lock(keymutex, 1);
     prev_p = NULL;
     for (p = keyhead; p != NULL; p = p->next) {
-        if (p->id == id && p->key == key) {
+        if (p->id == id && p->key == key)
-            if (update)
-                p->value = value;
             goto Done;
-        }
         /* Sanity check.  These states should never happen but if
          * they do we must abort.  Otherwise we'll end up spinning in
          * in a tight loop with the lock held.  A similar check is done
@@ -230,7 +227,7 @@ find_key(int key, int update, void *value)
         if (p->next == keyhead)
             Py_FatalError("tls find_key: circular list(!)");
     }
-    if (!update && value == NULL) {
+    if (value == NULL) {
         assert(p == NULL);
         goto Done;
     }
@@ -282,12 +279,19 @@ PyThread_delete_key(int key)
     PyThread_release_lock(keymutex);
 }
 
+/* Confusing:  If the current thread has an association for key,
+ * value is ignored, and 0 is returned.  Else an attempt is made to create
+ * an association of key to value for the current thread.  0 is returned
+ * if that succeeds, but -1 is returned if there's not enough memory
+ * to create the association.  value must not be NULL.
+ */
 int
 PyThread_set_key_value(int key, void *value)
 {
     struct key *p;
 
-    p = find_key(key, 1, value);
+    assert(value != NULL);
+    p = find_key(key, value);
     if (p == NULL)
         return -1;
     else
@@ -300,7 +304,7 @@ PyThread_set_key_value(int key, void *value)
 void *
 PyThread_get_key_value(int key)
 {
-    struct key *p = find_key(key, 0, NULL);
+    struct key *p = find_key(key, NULL);
 
     if (p == NULL)
         return NULL;

Python/thread_nt.h

@@ -389,11 +389,20 @@ PyThread_delete_key(int key)
     TlsFree(key);
 }
 
+/* We must be careful to emulate the strange semantics implemented in thread.c,
+ * where the value is only set if it hasn't been set before.
+ */
 int
 PyThread_set_key_value(int key, void *value)
 {
     BOOL ok;
+    void *oldvalue;
 
+    assert(value != NULL);
+    oldvalue = TlsGetValue(key);
+    if (oldvalue != NULL)
+        /* ignore value if already set */
+        return 0;
     ok = TlsSetValue(key, value);
     if (!ok)
         return -1;

Python/thread_pthread.h

@@ -627,6 +627,9 @@ int
 PyThread_set_key_value(int key, void *value)
 {
     int fail;
+    void *oldValue = pthread_getspecific(key);
+    if (oldValue != NULL)
+        return 0;
     fail = pthread_setspecific(key, value);
     return fail ? -1 : 0;
 }