mirror of https://github.com/python/cpython
92 lines
2.6 KiB
C
92 lines
2.6 KiB
C
#ifndef Py_INTERNAL_CONDVAR_H
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#define Py_INTERNAL_CONDVAR_H
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#ifndef Py_BUILD_CORE
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# error "this header requires Py_BUILD_CORE define"
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#endif
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#include "pycore_pythread.h" // _POSIX_THREADS
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#ifdef _POSIX_THREADS
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/*
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* POSIX support
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*/
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#define Py_HAVE_CONDVAR
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#ifdef HAVE_PTHREAD_H
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# include <pthread.h> // pthread_mutex_t
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#endif
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#define PyMUTEX_T pthread_mutex_t
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#define PyCOND_T pthread_cond_t
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#elif defined(NT_THREADS)
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/*
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* Windows (XP, 2003 server and later, as well as (hopefully) CE) support
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*
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* Emulated condition variables ones that work with XP and later, plus
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* example native support on VISTA and onwards.
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*/
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#define Py_HAVE_CONDVAR
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/* include windows if it hasn't been done before */
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#define WIN32_LEAN_AND_MEAN
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#include <windows.h> // CRITICAL_SECTION
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/* options */
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/* non-emulated condition variables are provided for those that want
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* to target Windows Vista. Modify this macro to enable them.
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*/
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#ifndef _PY_EMULATED_WIN_CV
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#define _PY_EMULATED_WIN_CV 1 /* use emulated condition variables */
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#endif
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/* fall back to emulation if not targeting Vista */
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#if !defined NTDDI_VISTA || NTDDI_VERSION < NTDDI_VISTA
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#undef _PY_EMULATED_WIN_CV
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#define _PY_EMULATED_WIN_CV 1
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#endif
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#if _PY_EMULATED_WIN_CV
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typedef CRITICAL_SECTION PyMUTEX_T;
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/* The ConditionVariable object. From XP onwards it is easily emulated
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with a Semaphore.
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Semaphores are available on Windows XP (2003 server) and later.
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We use a Semaphore rather than an auto-reset event, because although
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an auto-reset event might appear to solve the lost-wakeup bug (race
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condition between releasing the outer lock and waiting) because it
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maintains state even though a wait hasn't happened, there is still
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a lost wakeup problem if more than one thread are interrupted in the
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critical place. A semaphore solves that, because its state is
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counted, not Boolean.
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Because it is ok to signal a condition variable with no one
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waiting, we need to keep track of the number of
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waiting threads. Otherwise, the semaphore's state could rise
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without bound. This also helps reduce the number of "spurious wakeups"
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that would otherwise happen.
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*/
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typedef struct _PyCOND_T
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{
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HANDLE sem;
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int waiting; /* to allow PyCOND_SIGNAL to be a no-op */
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} PyCOND_T;
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#else /* !_PY_EMULATED_WIN_CV */
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/* Use native Win7 primitives if build target is Win7 or higher */
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/* SRWLOCK is faster and better than CriticalSection */
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typedef SRWLOCK PyMUTEX_T;
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typedef CONDITION_VARIABLE PyCOND_T;
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#endif /* _PY_EMULATED_WIN_CV */
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#endif /* _POSIX_THREADS, NT_THREADS */
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#endif /* Py_INTERNAL_CONDVAR_H */
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