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bpo-29871: Replace old condition variable emulation on Windows with o… #756

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63b5b5e
bpo-29871: Replace old condition variable emulation on Windows with o…
MojoVampire Mar 22, 2017
ed5655e
Merge branch 'master' into fix-issue-29871
zooba May 24, 2017
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3 changes: 3 additions & 0 deletions Misc/NEWS
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,9 @@ What's New in Python 3.7.0 alpha 1?
Core and Builtins
-----------------

- bpo-29871: Replace old condition variable emulation on Windows with
optimized locking primitives added in Windows Vista.

- bpo-27945: Fixed various segfaults with dict when input collections are
mutated during searching, inserting or comparing. Based on patches by
Duane Griffin and Tim Mitchell.
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17 changes: 9 additions & 8 deletions Python/condvar.h
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Expand Up @@ -124,11 +124,12 @@ PyCOND_TIMEDWAIT(PyCOND_T *cond, PyMUTEX_T *mut, long long us)
#include <windows.h>

/* options */
/* non-emulated condition variables are provided for those that want
* to target Windows Vista. Modify this macro to enable them.
/* As of 3.5, we only support Windows Vista and newer,
* so we default to building using the non-emulated condition variables
* Set this macro to 1 to explicitly use emulated condition variables
*/
#ifndef _PY_EMULATED_WIN_CV
#define _PY_EMULATED_WIN_CV 1 /* use emulated condition variables */
#define _PY_EMULATED_WIN_CV 0 /* use emulated condition variables */
#endif

/* fall back to emulation if not targeting Vista */
Expand Down Expand Up @@ -306,7 +307,7 @@ PyCOND_BROADCAST(PyCOND_T *cv)

#else

/* Use native Win7 primitives if build target is Win7 or higher */
/* Use native Vista primitives if build target is Vista or higher */

/* SRWLOCK is faster and better than CriticalSection */
typedef SRWLOCK PyMUTEX_T;
Expand Down Expand Up @@ -359,13 +360,13 @@ PyCOND_WAIT(PyCOND_T *cv, PyMUTEX_T *cs)
return SleepConditionVariableSRW(cv, cs, INFINITE, 0) ? 0 : -1;
}

/* This implementation makes no distinction about timeouts. Signal
* 2 to indicate that we don't know.
*/
Py_LOCAL_INLINE(int)
PyCOND_TIMEDWAIT(PyCOND_T *cv, PyMUTEX_T *cs, long long us)
{
return SleepConditionVariableSRW(cv, cs, (DWORD)(us/1000), 0) ? 2 : -1;
if (SleepConditionVariableSRW(cv, cs, (DWORD)(us/1000), 0))
return 0;

return GetLastError() == ERROR_TIMEOUT ? 1 : -1;
}

Py_LOCAL_INLINE(int)
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