mirror of
https://github.com/python/cpython.git
synced 2024-11-24 08:52:25 +01:00
31c90d5838
Critical sections are helpers to replace the global interpreter lock with finer grained locking. They provide similar guarantees to the GIL and avoid the deadlock risk that plain locking involves. Critical sections are implicitly ended whenever the GIL would be released. They are resumed when the GIL would be acquired. Nested critical sections behave as if the sections were interleaved.
101 lines
2.5 KiB
C
101 lines
2.5 KiB
C
#include "Python.h"
|
|
|
|
#include "pycore_lock.h"
|
|
#include "pycore_critical_section.h"
|
|
|
|
static_assert(_Alignof(_PyCriticalSection) >= 4,
|
|
"critical section must be aligned to at least 4 bytes");
|
|
|
|
void
|
|
_PyCriticalSection_BeginSlow(_PyCriticalSection *c, PyMutex *m)
|
|
{
|
|
PyThreadState *tstate = _PyThreadState_GET();
|
|
c->mutex = NULL;
|
|
c->prev = (uintptr_t)tstate->critical_section;
|
|
tstate->critical_section = (uintptr_t)c;
|
|
|
|
_PyMutex_LockSlow(m);
|
|
c->mutex = m;
|
|
}
|
|
|
|
void
|
|
_PyCriticalSection2_BeginSlow(_PyCriticalSection2 *c, PyMutex *m1, PyMutex *m2,
|
|
int is_m1_locked)
|
|
{
|
|
PyThreadState *tstate = _PyThreadState_GET();
|
|
c->base.mutex = NULL;
|
|
c->mutex2 = NULL;
|
|
c->base.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->base.mutex = m1;
|
|
c->mutex2 = m2;
|
|
}
|
|
|
|
static _PyCriticalSection *
|
|
untag_critical_section(uintptr_t tag)
|
|
{
|
|
return (_PyCriticalSection *)(tag & ~_Py_CRITICAL_SECTION_MASK);
|
|
}
|
|
|
|
// Release all locks held by critical sections. This is called by
|
|
// _PyThreadState_Detach.
|
|
void
|
|
_PyCriticalSection_SuspendAll(PyThreadState *tstate)
|
|
{
|
|
uintptr_t *tagptr = &tstate->critical_section;
|
|
while (_PyCriticalSection_IsActive(*tagptr)) {
|
|
_PyCriticalSection *c = untag_critical_section(*tagptr);
|
|
|
|
if (c->mutex) {
|
|
PyMutex_Unlock(c->mutex);
|
|
if ((*tagptr & _Py_CRITICAL_SECTION_TWO_MUTEXES)) {
|
|
_PyCriticalSection2 *c2 = (_PyCriticalSection2 *)c;
|
|
if (c2->mutex2) {
|
|
PyMutex_Unlock(c2->mutex2);
|
|
}
|
|
}
|
|
}
|
|
|
|
*tagptr |= _Py_CRITICAL_SECTION_INACTIVE;
|
|
tagptr = &c->prev;
|
|
}
|
|
}
|
|
|
|
void
|
|
_PyCriticalSection_Resume(PyThreadState *tstate)
|
|
{
|
|
uintptr_t p = tstate->critical_section;
|
|
_PyCriticalSection *c = untag_critical_section(p);
|
|
assert(!_PyCriticalSection_IsActive(p));
|
|
|
|
PyMutex *m1 = c->mutex;
|
|
c->mutex = NULL;
|
|
|
|
PyMutex *m2 = NULL;
|
|
_PyCriticalSection2 *c2 = NULL;
|
|
if ((p & _Py_CRITICAL_SECTION_TWO_MUTEXES)) {
|
|
c2 = (_PyCriticalSection2 *)c;
|
|
m2 = c2->mutex2;
|
|
c2->mutex2 = NULL;
|
|
}
|
|
|
|
if (m1) {
|
|
PyMutex_Lock(m1);
|
|
}
|
|
if (m2) {
|
|
PyMutex_Lock(m2);
|
|
}
|
|
|
|
c->mutex = m1;
|
|
if (m2) {
|
|
c2->mutex2 = m2;
|
|
}
|
|
|
|
tstate->critical_section &= ~_Py_CRITICAL_SECTION_INACTIVE;
|
|
}
|