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gh-100227: Add a Granular Lock for _PyRuntime.imports.extensions.dict #103460

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merged 3 commits into from Apr 25, 2023
Merged

gh-100227: Add a Granular Lock for _PyRuntime.imports.extensions.dict #103460

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02b681c
Add a granular lock for _PyRuntime.imports.extensions.
ericsnowcurrently Apr 6, 2023
1755379
Use the lock.
ericsnowcurrently Apr 6, 2023
ea1e7ee
Merge branch 'main' into extensions-lock
ericsnowcurrently Apr 25, 2023
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2 changes: 2 additions & 0 deletions Include/internal/pycore_import.h
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Expand Up @@ -19,6 +19,8 @@ struct _import_runtime_state {
used exclusively for when the extensions dict is access/modified
from an arbitrary thread. */
PyThreadState main_tstate;
/* A lock to guard the dict. */
PyThread_type_lock mutex;
/* A dict mapping (filename, name) to PyModuleDef for modules.
Only legacy (single-phase init) extension modules are added
and only if they support multiple initialization (m_size >- 0)
Expand Down
13 changes: 10 additions & 3 deletions Python/import.c
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Expand Up @@ -413,8 +413,11 @@ remove_module(PyThreadState *tstate, PyObject *name)
Py_ssize_t
_PyImport_GetNextModuleIndex(void)
{
PyThread_acquire_lock(EXTENSIONS.mutex, WAIT_LOCK);
LAST_MODULE_INDEX++;
return LAST_MODULE_INDEX;
Py_ssize_t index = LAST_MODULE_INDEX;
PyThread_release_lock(EXTENSIONS.mutex);
return index;
}

static const char *
Expand Down Expand Up @@ -703,21 +706,25 @@ _PyImport_ClearModulesByIndex(PyInterpreterState *interp)
const char *
_PyImport_ResolveNameWithPackageContext(const char *name)
{
PyThread_acquire_lock(EXTENSIONS.mutex, WAIT_LOCK);
if (PKGCONTEXT != NULL) {
const char *p = strrchr(PKGCONTEXT, '.');
if (p != NULL && strcmp(name, p+1) == 0) {
name = PKGCONTEXT;
PKGCONTEXT = NULL;
}
}
PyThread_release_lock(EXTENSIONS.mutex);
return name;
}

const char *
_PyImport_SwapPackageContext(const char *newcontext)
{
PyThread_acquire_lock(EXTENSIONS.mutex, WAIT_LOCK);
const char *oldcontext = PKGCONTEXT;
PKGCONTEXT = newcontext;
PyThread_release_lock(EXTENSIONS.mutex);
return oldcontext;
}

Expand Down Expand Up @@ -865,13 +872,13 @@ gets even messier.
static inline void
extensions_lock_acquire(void)
{
// XXX For now the GIL is sufficient.
PyThread_acquire_lock(_PyRuntime.imports.extensions.mutex, WAIT_LOCK);
}

static inline void
extensions_lock_release(void)
{
// XXX For now the GIL is sufficient.
PyThread_release_lock(_PyRuntime.imports.extensions.mutex);
}

/* Magic for extension modules (built-in as well as dynamically
Expand Down
5 changes: 4 additions & 1 deletion Python/pystate.c
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Expand Up @@ -380,7 +380,7 @@ _Py_COMP_DIAG_IGNORE_DEPR_DECLS
static const _PyRuntimeState initial = _PyRuntimeState_INIT(_PyRuntime);
_Py_COMP_DIAG_POP

#define NUMLOCKS 4
#define NUMLOCKS 5

static int
alloc_for_runtime(PyThread_type_lock locks[NUMLOCKS])
Expand Down Expand Up @@ -434,6 +434,7 @@ init_runtime(_PyRuntimeState *runtime,
&runtime->xidregistry.mutex,
&runtime->getargs.mutex,
&runtime->unicode_state.ids.lock,
&runtime->imports.extensions.mutex,
};
for (int i = 0; i < NUMLOCKS; i++) {
assert(locks[i] != NULL);
Expand Down Expand Up @@ -518,6 +519,7 @@ _PyRuntimeState_Fini(_PyRuntimeState *runtime)
&runtime->xidregistry.mutex,
&runtime->getargs.mutex,
&runtime->unicode_state.ids.lock,
&runtime->imports.extensions.mutex,
};
for (int i = 0; i < NUMLOCKS; i++) {
FREE_LOCK(*lockptrs[i]);
Expand Down Expand Up @@ -546,6 +548,7 @@ _PyRuntimeState_ReInitThreads(_PyRuntimeState *runtime)
&runtime->xidregistry.mutex,
&runtime->getargs.mutex,
&runtime->unicode_state.ids.lock,
&runtime->imports.extensions.mutex,
};
int reinit_err = 0;
for (int i = 0; i < NUMLOCKS; i++) {
Expand Down