8000 [3.12] gh-105699: Use a Thread-Local Variable for PKGCONTEXT (gh-1057… · python/cpython@bc997b3 · GitHub
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[3.12] gh-105699: Use a Thread-Local Variable for PKGCONTEXT (gh-105740) (gh-105765)
This fixes a race during import. The existing _PyRuntimeState.imports.pkgcontext is shared between interpreters, and occasionally this would cause a crash when multiple interpreters were importing extensions modules at the same time. To solve this we add a thread-local variable for the value. We also leave the existing state (and infrequent race) in place for platforms that do not support thread-local variables. (cherry picked from commit b87d288) Co-authored-by: Eric Snow <ericsnowcurrently@gmail.com>
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‎Python/import.c

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@@ -703,28 +703,43 @@ _PyImport_ClearModulesByIndex(PyInterpreterState *interp)
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_PyRuntime.imports.pkgcontext, and PyModule_Create*() will
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substitute this (if the name actually matches).
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*/
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#ifdef HAVE_THREAD_LOCAL
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_Py_thread_local const char *pkgcontext = NULL;
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# undef PKGCONTEXT
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# define PKGCONTEXT pkgcontext
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#endif
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const char *
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_PyImport_ResolveNameWithPackageContext(const char *name)
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{
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#ifndef HAVE_THREAD_LOCAL
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PyThread_acquire_lock(EXTENSIONS.mutex, WAIT_LOCK);
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#endif
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if (PKGCONTEXT != NULL) {
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const char *p = strrchr(PKGCONTEXT, '.');
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if (p != NULL && strcmp(name, p+1) == 0) {
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name = PKGCONTEXT;
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PKGCONTEXT = NULL;
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}
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}
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#ifndef HAVE_THREAD_LOCAL
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PyThread_release_lock(EXTENSIONS.mutex);
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#endif
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return name;
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}
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const char *
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_PyImport_SwapPackageContext(const char *newcontext)
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{
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#ifndef HAVE_THREAD_LOCAL
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PyThread_acquire_lock(EXTENSIONS.mutex, WAIT_LOCK);
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#endif
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const char *oldcontext = PKGCONTEXT;
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PKGCONTEXT = newcontext;
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#ifndef HAVE_THREAD_LOCAL
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PyThread_release_lock(EXTENSIONS.mutex);
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#endif
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return oldcontext;
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}
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‎Tools/c-analyzer/c_parser/parser/_regexes.py

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@@ -58,6 +58,7 @@ def _ind(text, level=1, edges='both'):
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extern |
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register |
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static |
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_Thread_local |
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typedef |
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const |
@@ -137,7 +138,7 @@ def _ind(text, level=1, edges='both'):
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#######################################
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# variable declarations
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_STORAGE = 'auto register static extern'.split()
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_STORAGE = 'auto register static extern _Thread_local'.split()
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STORAGE_CLASS = rf'(?: \b (?: {" | ".join(_STORAGE)} ) \b )'
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TYPE_QUALIFIER = r'(?: \b (?: const | volatile ) \b )'
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PTR_QUALIFIER = rf'(?: [*] (?: \s* {TYPE_QUALIFIER} )? )'

‎Tools/c-analyzer/c_parser/preprocessor/gcc.py

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@@ -219,6 +219,7 @@ def _strip_directives(line, partial=0):
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line = line[m.end():]
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line = re.sub(r'__extension__', '', line)
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line = re.sub(r'__thread\b', '_Thread_local', line)
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while (m := COMPILER_DIRECTIVE_RE.match(line)):
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before, _, _, closed = m.groups()

‎Tools/c-analyzer/cpython/ignored.tsv

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@@ -168,6 +168,12 @@ Modules/_xxinterpchannelsmodule.c - _globals -
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Python/pyfpe.c - PyFPE_counter -
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##-----------------------
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## thread-local variables
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Python/import.c - pkgcontext -
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Python/pystate.c - _Py_tss_tstate -
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##-----------------------
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## should be const
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# XXX Make them const.

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