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180d417e9f
Add a fast path to (single-mutex) critical section locking _iff_ the mutex is already held by the currently active, top-most critical section of this thread. This can matter a lot for indirectly recursive critical sections without intervening critical sections.
158 lines
3.7 KiB
C
158 lines
3.7 KiB
C
#include "Python.h"
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#include "pycore_lock.h"
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#include "pycore_critical_section.h"
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#ifdef Py_GIL_DISABLED
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static_assert(_Alignof(PyCriticalSection) >= 4,
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"critical section must be aligned to at least 4 bytes");
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#endif
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#ifdef Py_GIL_DISABLED
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static PyCriticalSection *
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untag_critical_section(uintptr_t tag)
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{
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return (PyCriticalSection *)(tag & ~_Py_CRITICAL_SECTION_MASK);
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}
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#endif
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void
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_PyCriticalSection_BeginSlow(PyCriticalSection *c, PyMutex *m)
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{
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#ifdef Py_GIL_DISABLED
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PyThreadState *tstate = _PyThreadState_GET();
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// As an optimisation for locking the same object recursively, skip
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// locking if the mutex is currently locked by the top-most critical
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// section.
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if (tstate->critical_section &&
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untag_critical_section(tstate->critical_section)->_cs_mutex == m) {
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c->_cs_mutex = NULL;
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c->_cs_prev = 0;
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return;
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}
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c->_cs_mutex = NULL;
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c->_cs_prev = (uintptr_t)tstate->critical_section;
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tstate->critical_section = (uintptr_t)c;
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PyMutex_Lock(m);
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c->_cs_mutex = m;
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#endif
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}
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void
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_PyCriticalSection2_BeginSlow(PyCriticalSection2 *c, PyMutex *m1, PyMutex *m2,
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int is_m1_locked)
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{
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#ifdef Py_GIL_DISABLED
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PyThreadState *tstate = _PyThreadState_GET();
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c->_cs_base._cs_mutex = NULL;
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c->_cs_mutex2 = NULL;
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c->_cs_base._cs_prev = tstate->critical_section;
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tstate->critical_section = (uintptr_t)c | _Py_CRITICAL_SECTION_TWO_MUTEXES;
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if (!is_m1_locked) {
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PyMutex_Lock(m1);
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}
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PyMutex_Lock(m2);
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c->_cs_base._cs_mutex = m1;
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c->_cs_mutex2 = m2;
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#endif
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}
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// Release all locks held by critical sections. This is called by
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// _PyThreadState_Detach.
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void
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_PyCriticalSection_SuspendAll(PyThreadState *tstate)
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{
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#ifdef Py_GIL_DISABLED
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uintptr_t *tagptr = &tstate->critical_section;
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while (_PyCriticalSection_IsActive(*tagptr)) {
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PyCriticalSection *c = untag_critical_section(*tagptr);
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if (c->_cs_mutex) {
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PyMutex_Unlock(c->_cs_mutex);
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if ((*tagptr & _Py_CRITICAL_SECTION_TWO_MUTEXES)) {
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PyCriticalSection2 *c2 = (PyCriticalSection2 *)c;
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if (c2->_cs_mutex2) {
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PyMutex_Unlock(c2->_cs_mutex2);
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}
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}
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}
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*tagptr |= _Py_CRITICAL_SECTION_INACTIVE;
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tagptr = &c->_cs_prev;
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}
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#endif
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}
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void
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_PyCriticalSection_Resume(PyThreadState *tstate)
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{
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#ifdef Py_GIL_DISABLED
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uintptr_t p = tstate->critical_section;
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PyCriticalSection *c = untag_critical_section(p);
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assert(!_PyCriticalSection_IsActive(p));
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PyMutex *m1 = c->_cs_mutex;
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c->_cs_mutex = NULL;
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PyMutex *m2 = NULL;
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PyCriticalSection2 *c2 = NULL;
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if ((p & _Py_CRITICAL_SECTION_TWO_MUTEXES)) {
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c2 = (PyCriticalSection2 *)c;
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m2 = c2->_cs_mutex2;
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c2->_cs_mutex2 = NULL;
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}
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if (m1) {
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PyMutex_Lock(m1);
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}
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if (m2) {
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PyMutex_Lock(m2);
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}
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c->_cs_mutex = m1;
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if (m2) {
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c2->_cs_mutex2 = m2;
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}
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tstate->critical_section &= ~_Py_CRITICAL_SECTION_INACTIVE;
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#endif
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}
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#undef PyCriticalSection_Begin
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void
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PyCriticalSection_Begin(PyCriticalSection *c, PyObject *op)
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{
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#ifdef Py_GIL_DISABLED
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_PyCriticalSection_Begin(c, op);
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#endif
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}
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#undef PyCriticalSection_End
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void
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PyCriticalSection_End(PyCriticalSection *c)
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{
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#ifdef Py_GIL_DISABLED
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_PyCriticalSection_End(c);
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#endif
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}
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#undef PyCriticalSection2_Begin
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void
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PyCriticalSection2_Begin(PyCriticalSection2 *c, PyObject *a, PyObject *b)
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{
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#ifdef Py_GIL_DISABLED
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_PyCriticalSection2_Begin(c, a, b);
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#endif
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}
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#undef PyCriticalSection2_End
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void
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PyCriticalSection2_End(PyCriticalSection2 *c)
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{
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#ifdef Py_GIL_DISABLED
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_PyCriticalSection2_End(c);
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#endif
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}
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