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gh-119344: Make critical section API public (#119353)

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This makes the following macros public as part of the non-limited C-API for
locking a single object or two objects at once.

* `Py_BEGIN_CRITICAL_SECTION(op)` / `Py_END_CRITICAL_SECTION()`
* `Py_BEGIN_CRITICAL_SECTION2(a, b)` / `Py_END_CRITICAL_SECTION2()`

The supporting functions and structs used by the macros are also exposed for
cases where C macros are not available.
This commit is contained in:
Sam Gross 2024-06-21 15:50:18 -04:00 • committed by GitHub
parent 03fa2df927
commit 8f17d69b7b
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GPG key ID: B5690EEEBB952194
15 changed files with 459 additions and 225 deletions
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106
Python/critical_section.c
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@ -3,85 +3,96 @@
#include "pycore_lock.h"
#include "pycore_critical_section.h"
static_assert(_Alignof(_PyCriticalSection) >= 4,
#ifdef Py_GIL_DISABLED
static_assert(_Alignof(PyCriticalSection) >= 4,
"critical section must be aligned to at least 4 bytes");
#endif
void
_PyCriticalSection_BeginSlow(_PyCriticalSection *c, PyMutex *m)
_PyCriticalSection_BeginSlow(PyCriticalSection *c, PyMutex *m)
{
#ifdef Py_GIL_DISABLED
PyThreadState *tstate = _PyThreadState_GET();
c->mutex = NULL;
c->prev = (uintptr_t)tstate->critical_section;
c->_cs_mutex = NULL;
c->_cs_prev = (uintptr_t)tstate->critical_section;
tstate->critical_section = (uintptr_t)c;
PyMutex_Lock(m);
c->mutex = m;
c->_cs_mutex = m;
#endif
}
void
_PyCriticalSection2_BeginSlow(_PyCriticalSection2 *c, PyMutex *m1, PyMutex *m2,
_PyCriticalSection2_BeginSlow(PyCriticalSection2 *c, PyMutex *m1, PyMutex *m2,
int is_m1_locked)
{
#ifdef Py_GIL_DISABLED
PyThreadState *tstate = _PyThreadState_GET();
c->base.mutex = NULL;
c->mutex2 = NULL;
c->base.prev = tstate->critical_section;
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->base.mutex = m1;
c->mutex2 = m2;
c->_cs_base._cs_mutex = m1;
c->_cs_mutex2 = m2;
#endif
}
static _PyCriticalSection *
#ifdef Py_GIL_DISABLED
static PyCriticalSection *
untag_critical_section(uintptr_t tag)
{
return (_PyCriticalSection *)(tag & ~_Py_CRITICAL_SECTION_MASK);
return (PyCriticalSection *)(tag & ~_Py_CRITICAL_SECTION_MASK);
}
#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);
PyCriticalSection *c = untag_critical_section(*tagptr);
if (c->mutex) {
PyMutex_Unlock(c->mutex);
if (c->_cs_mutex) {
PyMutex_Unlock(c->_cs_mutex);
if ((*tagptr & _Py_CRITICAL_SECTION_TWO_MUTEXES)) {
_PyCriticalSection2 *c2 = (_PyCriticalSection2 *)c;
if (c2->mutex2) {
PyMutex_Unlock(c2->mutex2);
PyCriticalSection2 *c2 = (PyCriticalSection2 *)c;
if (c2->_cs_mutex2) {
PyMutex_Unlock(c2->_cs_mutex2);
}
}
}
*tagptr |= _Py_CRITICAL_SECTION_INACTIVE;
tagptr = &c->prev;
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);
PyCriticalSection *c = untag_critical_section(p);
assert(!_PyCriticalSection_IsActive(p));
PyMutex *m1 = c->mutex;
c->mutex = NULL;
PyMutex *m1 = c->_cs_mutex;
c->_cs_mutex = NULL;
PyMutex *m2 = NULL;
_PyCriticalSection2 *c2 = NULL;
PyCriticalSection2 *c2 = NULL;
if ((p & _Py_CRITICAL_SECTION_TWO_MUTEXES)) {
c2 = (_PyCriticalSection2 *)c;
m2 = c2->mutex2;
c2->mutex2 = NULL;
c2 = (PyCriticalSection2 *)c;
m2 = c2->_cs_mutex2;
c2->_cs_mutex2 = NULL;
}
if (m1) {
@ -91,10 +102,47 @@ _PyCriticalSection_Resume(PyThreadState *tstate)
PyMutex_Lock(m2);
}
c->mutex = m1;
c->_cs_mutex = m1;
if (m2) {
c2->mutex2 = 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(c, op);
#endif
}
#undef PyCriticalSection_End
void
PyCriticalSection_End(PyCriticalSection *c)
{
#ifdef Py_GIL_DISABLED
_PyCriticalSection_End(c);
#endif
}
#undef PyCriticalSection2_Begin
void
PyCriticalSection2_Begin(PyCriticalSection2 *c, PyObject *a, PyObject *b)
{
#ifdef Py_GIL_DISABLED
_PyCriticalSection2_Begin(c, a, b);
#endif
}
#undef PyCriticalSection2_End
void
PyCriticalSection2_End(PyCriticalSection2 *c)
{
#ifdef Py_GIL_DISABLED
_PyCriticalSection2_End(c);
#endif
}