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gh-111956: Add thread-safe one-time initialization. (gh-111960)

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Sam Gross 2023-11-16 14:19:54 -05:00 • committed by GitHub
parent f66afa395a
commit 446f18a911
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11 changed files with 1061 additions and 955 deletions
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46
Python/getargs.c
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@ -1877,8 +1877,9 @@ new_kwtuple(const char * const *keywords, int total, int pos)
}
static int
_parser_init(struct _PyArg_Parser *parser)
_parser_init(void *arg)
{
struct _PyArg_Parser *parser = (struct _PyArg_Parser *)arg;
const char * const *keywords = parser->keywords;
assert(keywords != NULL);
assert(parser->pos == 0 &&
@ -1889,7 +1890,7 @@ _parser_init(struct _PyArg_Parser *parser)
int len, pos;
if (scan_keywords(keywords, &len, &pos) < 0) {
return 0;
return -1;
}
const char *fname, *custommsg = NULL;
@ -1898,7 +1899,7 @@ _parser_init(struct _PyArg_Parser *parser)
assert(parser->fname == NULL);
if (parse_format(parser->format, len, pos,
&fname, &custommsg, &min, &max) < 0) {
return 0;
return -1;
}
}
else {
@ -1911,7 +1912,7 @@ _parser_init(struct _PyArg_Parser *parser)
if (kwtuple == NULL) {
kwtuple = new_kwtuple(keywords, len, pos);
if (kwtuple == NULL) {
return 0;
return -1;
}
owned = 1;
}
@ -1925,40 +1926,27 @@ _parser_init(struct _PyArg_Parser *parser)
parser->min = min;
parser->max = max;
parser->kwtuple = kwtuple;
parser->initialized = owned ? 1 : -1;
parser->is_kwtuple_owned = owned;
assert(parser->next == NULL);
parser->next = _PyRuntime.getargs.static_parsers;
_PyRuntime.getargs.static_parsers = parser;
return 1;
parser->next = _Py_atomic_load_ptr(&_PyRuntime.getargs.static_parsers);
do {
// compare-exchange updates parser->next on failure
} while (_Py_atomic_compare_exchange_ptr(&_PyRuntime.getargs.static_parsers,
&parser->next, parser));
return 0;
}
static int
parser_init(struct _PyArg_Parser *parser)
{
// volatile as it can be modified by other threads
// and should not be optimized or reordered by compiler
if (*((volatile int *)&parser->initialized)) {
assert(parser->kwtuple != NULL);
return 1;
}
PyThread_acquire_lock(_PyRuntime.getargs.mutex, WAIT_LOCK);
// Check again if another thread initialized the parser
// while we were waiting for the lock.
if (*((volatile int *)&parser->initialized)) {
assert(parser->kwtuple != NULL);
PyThread_release_lock(_PyRuntime.getargs.mutex);
return 1;
}
int ret = _parser_init(parser);
PyThread_release_lock(_PyRuntime.getargs.mutex);
return ret;
return _PyOnceFlag_CallOnce(&parser->once, &_parser_init, parser);
}
static void
parser_clear(struct _PyArg_Parser *parser)
{
if (parser->initialized == 1) {
if (parser->is_kwtuple_owned) {
Py_CLEAR(parser->kwtuple);
}
}
@ -2025,7 +2013,7 @@ vgetargskeywordsfast_impl(PyObject *const *args, Py_ssize_t nargs,
return 0;
}
if (!parser_init(parser)) {
if (parser_init(parser) < 0) {
return 0;
}
@ -2258,7 +2246,7 @@ _PyArg_UnpackKeywords(PyObject *const *args, Py_ssize_t nargs,
args = buf;
}
if (!parser_init(parser)) {
if (parser_init(parser) < 0) {
return NULL;
}
@ -2435,7 +2423,7 @@ _PyArg_UnpackKeywordsWithVararg(PyObject *const *args, Py_ssize_t nargs,
args = buf;
}
if (!parser_init(parser)) {
if (parser_init(parser) < 0) {
return NULL;
}