#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

}