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#include "Python.h"

#include "pycore_critical_section.h"

#include "pycore_interp.h"

#include "pycore_lock.h"

#ifdef Py_GIL_DISABLED

static_assert(_Alignof(PyCriticalSection) >= 4,

"critical section must be aligned to at least 4 bytes");

#endif

#ifdef Py_GIL_DISABLED

static PyCriticalSection *

untag_critical_section(uintptr_t tag)

{

return (PyCriticalSection *)(tag & ~_Py_CRITICAL_SECTION_MASK);

}

#endif

void

_PyCriticalSection_BeginSlow(PyThreadState *tstate, PyCriticalSection *c, PyMutex *m)

{

#ifdef Py_GIL_DISABLED

// As an optimisation for locking the same object recursively, skip

// locking if the mutex is currently locked by the top-most critical

// section.

// If the top-most critical section is a two-mutex critical section,

// then locking is skipped if either mutex is m.

if (tstate->critical_section) {

PyCriticalSection *prev = untag_critical_section(tstate->critical_section);

if (prev->_cs_mutex == m) {

c->_cs_mutex = NULL;

c->_cs_prev = 0;

return;

}

if (tstate->critical_section & _Py_CRITICAL_SECTION_TWO_MUTEXES) {

PyCriticalSection2 *prev2 = (PyCriticalSection2 *)

untag_critical_section(tstate->critical_section);

if (prev2->_cs_mutex2 == m) {

c->_cs_mutex = NULL;

c->_cs_prev = 0;

return;

}

// If the world is stopped, we don't need to acquire the lock because

// there are no other threads that could be accessing the object.

// Without this check, acquiring a critical section while the world is

// stopped could lead to a deadlock.

if (tstate->interp->stoptheworld.world_stopped) {

c->_cs_mutex = NULL;

c->_cs_prev = 0;

return;

}

c->_cs_mutex = NULL;

c->_cs_prev = (uintptr_t)tstate->critical_section;

tstate->critical_section = (uintptr_t)c;

PyMutex_Lock(m);

c->_cs_mutex = m;

#endif

}

void

_PyCriticalSection2_BeginSlow(PyThreadState *tstate, PyCriticalSection2 *c, PyMutex *m1, PyMutex *m2,

int is_m1_locked)

{

#ifdef Py_GIL_DISABLED

if (tstate->interp->stoptheworld.world_stopped) {

c->_cs_base._cs_mutex = NULL;

c->_cs_mutex2 = NULL;

c->_cs_base._cs_prev = 0;

return;

}

// Same optimization as in _PyCriticalSection_BeginSlow: skip locking when

// recursively acquiring the same locks.

if (tstate->critical_section &&

tstate->critical_section & _Py_CRITICAL_SECTION_TWO_MUTEXES) {

PyCriticalSection2 *prev2 = (PyCriticalSection2 *)

untag_critical_section(tstate->critical_section);

assert((uintptr_t)m1 < (uintptr_t)m2);

assert((uintptr_t)prev2->_cs_base._cs_mutex <

(uintptr_t)prev2->_cs_mutex2);

if (prev2->_cs_base._cs_mutex == m1 && prev2->_cs_mutex2 == m2) {

c->_cs_base._cs_mutex = NULL;

c->_cs_mutex2 = NULL;

c->_cs_base._cs_prev = 0;

return;

}

c->_cs_base._cs_mutex = NULL;

c->_cs_mutex2 = NULL;

c->_cs_base._cs_prev = tstate->critical_section;

tstate->critical_section = (uintptr_t)c | _Py_CRITICAL_SECTION_TWO_MUTEXES;

if (!is_m1_locked) {

PyMutex_Lock(m1);

}

PyMutex_Lock(m2);

c->_cs_base._cs_mutex = m1;

c->_cs_mutex2 = m2;

#endif

}

// Release all locks held by critical sections. This is called by

// _PyThreadState_Detach.

void

_PyCriticalSection_SuspendAll(PyThreadState *tstate)

{

#ifdef Py_GIL_DISABLED

uintptr_t *tagptr = &tstate->critical_section;

while (_PyCriticalSection_IsActive(*tagptr)) {

PyCriticalSection *c = untag_critical_section(*tagptr);

if (c->_cs_mutex) {

PyMutex_Unlock(c->_cs_mutex);

if ((*tagptr & _Py_CRITICAL_SECTION_TWO_MUTEXES)) {

PyCriticalSection2 *c2 = (PyCriticalSection2 *)c;

if (c2->_cs_mutex2) {

PyMutex_Unlock(c2->_cs_mutex2);

}

*tagptr |= _Py_CRITICAL_SECTION_INACTIVE;

tagptr = &c->_cs_prev;

}

#endif

}

void

_PyCriticalSection_Resume(PyThreadState *tstate)

{

#ifdef Py_GIL_DISABLED

uintptr_t p = tstate->critical_section;

PyCriticalSection *c = untag_critical_section(p);

assert(!_PyCriticalSection_IsActive(p));

PyMutex *m1 = c->_cs_mutex;

c->_cs_mutex = NULL;

PyMutex *m2 = NULL;

PyCriticalSection2 *c2 = NULL;

if ((p & _Py_CRITICAL_SECTION_TWO_MUTEXES)) {

c2 = (PyCriticalSection2 *)c;

m2 = c2->_cs_mutex2;

c2->_cs_mutex2 = NULL;

}

if (m1) {

PyMutex_Lock(m1);

}

if (m2) {

PyMutex_Lock(m2);

}

c->_cs_mutex = m1;

if (m2) {

c2->_cs_mutex2 = m2;

}

tstate->critical_section &= ~_Py_CRITICAL_SECTION_INACTIVE;

#endif

}

#undef PyCriticalSection_Begin

void

PyCriticalSection_Begin(PyCriticalSection *c, PyObject *op)

{

#ifdef Py_GIL_DISABLED

_PyCriticalSection_Begin(_PyThreadState_GET(), c, op);

#endif

}

#undef PyCriticalSection_BeginMutex

void

PyCriticalSection_BeginMutex(PyCriticalSection *c, PyMutex *m)

{

#ifdef Py_GIL_DISABLED

_PyCriticalSection_BeginMutex(_PyThreadState_GET(), c, m);

#endif

}

#undef PyCriticalSection_End

void

PyCriticalSection_End(PyCriticalSection *c)

{

#ifdef Py_GIL_DISABLED

_PyCriticalSection_End(_PyThreadState_GET(), c);

#endif

}

#undef PyCriticalSection2_Begin

void

PyCriticalSection2_Begin(PyCriticalSection2 *c, PyObject *a, PyObject *b)

{

#ifdef Py_GIL_DISABLED

_PyCriticalSection2_Begin(_PyThreadState_GET(), c, a, b);

#endif

}

#undef PyCriticalSection2_BeginMutex

void

PyCriticalSection2_BeginMutex(PyCriticalSection2 *c, PyMutex *m1, PyMutex *m2)

{

#ifdef Py_GIL_DISABLED

_PyCriticalSection2_BeginMutex(_PyThreadState_GET(), c, m1, m2);

#endif

}

#undef PyCriticalSection2_End

void

PyCriticalSection2_End(PyCriticalSection2 *c)

{

#ifdef Py_GIL_DISABLED

_PyCriticalSection2_End(_PyThreadState_GET(), c);

#endif

}

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