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gh-100227: Lock Around Use of the Global "atexit" State #105514

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merged 2 commits into from
Jun 8, 2023
Merged

gh-100227: Lock Around Use of the Global "atexit" State #105514

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3cdbcdc
Factor out LOCKS_INIT().
ericsnowcurrently Jun 7, 2023
f1b6610
Add a granular lock for global atexit state.
ericsnowcurrently Jun 7, 2023
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1 change: 1 addition & 0 deletions Include/internal/pycore_atexit.h
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ extern "C" {
typedef void (*atexit_callbackfunc)(void);

struct _atexit_runtime_state {
PyThread_type_lock mutex;
#define NEXITFUNCS 32
atexit_callbackfunc callbacks[NEXITFUNCS];
int ncallbacks;
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17 changes: 14 additions & 3 deletions Python/pylifecycle.c
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Expand Up @@ -2973,24 +2973,35 @@ wait_for_thread_shutdown(PyThreadState *tstate)

int Py_AtExit(void (*func)(void))
{
if (_PyRuntime.atexit.ncallbacks >= NEXITFUNCS)
struct _atexit_runtime_state *state = &_PyRuntime.atexit;
PyThread_acquire_lock(state->mutex, WAIT_LOCK);
if (state->ncallbacks >= NEXITFUNCS) {
PyThread_release_lock(state->mutex);
return -1;
_PyRuntime.atexit.callbacks[_PyRuntime.atexit.ncallbacks++] = func;
}
state->callbacks[state->ncallbacks++] = func;
PyThread_release_lock(state->mutex);
return 0;
}

static void
call_ll_exitfuncs(_PyRuntimeState *runtime)
{
atexit_callbackfunc exitfunc;
struct _atexit_runtime_state *state = &runtime->atexit;

PyThread_acquire_lock(state->mutex, WAIT_LOCK);
while (state->ncallbacks > 0) {
/* pop last function from the list */
state->ncallbacks--;
atexit_callbackfunc exitfunc = state->callbacks[state->ncallbacks];
exitfunc = state->callbacks[state->ncallbacks];
state->callbacks[state->ncallbacks] = NULL;

PyThread_release_lock(state->mutex);
exitfunc();
PyThread_acquire_lock(state->mutex, WAIT_LOCK);
}
PyThread_release_lock(state->mutex);

fflush(stdout);
fflush(stderr);
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35 changes: 13 additions & 22 deletions Python/pystate.c
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Expand Up @@ -380,7 +380,16 @@ _Py_COMP_DIAG_IGNORE_DEPR_DECLS
static const _PyRuntimeState initial = _PyRuntimeState_INIT(_PyRuntime);
_Py_COMP_DIAG_POP

#define NUMLOCKS 5
#define NUMLOCKS 6
#define LOCKS_INIT(runtime) \
{ \
&(runtime)->interpreters.mutex, \
&(runtime)->xidregistry.mutex, \
&(runtime)->getargs.mutex, \
&(runtime)->unicode_state.ids.lock, \
&(runtime)->imports.extensions.mutex, \
&(runtime)->atexit.mutex, \
}

static int
alloc_for_runtime(PyThread_type_lock locks[NUMLOCKS])
Expand Down Expand Up @@ -427,13 +436,7 @@ init_runtime(_PyRuntimeState *runtime,

PyPreConfig_InitPythonConfig(&runtime->preconfig);

PyThread_type_lock *lockptrs[NUMLOCKS] = {
&runtime->interpreters.mutex,
&runtime->xidregistry.mutex,
&runtime->getargs.mutex,
&runtime->unicode_state.ids.lock,
&runtime->imports.extensions.mutex,
};
PyThread_type_lock *lockptrs[NUMLOCKS] = LOCKS_INIT(runtime);
for (int i = 0; i < NUMLOCKS; i++) {
assert(locks[i] != NULL);
*lockptrs[i] = locks[i];
Expand Down Expand Up @@ -512,13 +515,7 @@ _PyRuntimeState_Fini(_PyRuntimeState *runtime)
LOCK = NULL; \
}

PyThread_type_lock *lockptrs[NUMLOCKS] = {
&runtime->interpreters.mutex,
&runtime->xidregistry.mutex,
&runtime->getargs.mutex,
&runtime->unicode_state.ids.lock,
&runtime->imports.extensions.mutex,
};
PyThread_type_lock *lockptrs[NUMLOCKS] = LOCKS_INIT(runtime);
for (int i = 0; i < NUMLOCKS; i++) {
FREE_LOCK(*lockptrs[i]);
}
Expand All @@ -541,13 +538,7 @@ _PyRuntimeState_ReInitThreads(_PyRuntimeState *runtime)
PyMemAllocatorEx old_alloc;
_PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);

PyThread_type_lock *lockptrs[NUMLOCKS] = {
&runtime->interpreters.mutex,
&runtime->xidregistry.mutex,
&runtime->getargs.mutex,
&runtime->unicode_state.ids.lock,
&runtime->imports.extensions.mutex,
};
PyThread_type_lock *lockptrs[NUMLOCKS] = LOCKS_INIT(runtime);
int reinit_err = 0;
for (int i = 0; i < NUMLOCKS; i++) {
reinit_err += _PyThread_at_fork_reinit(lockptrs[i]);
Expand Down