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[3.10] bpo-41710: Fix PY_TIMEOUT_MAX value on Windows #28672

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[3.10] bpo-41710: Fix PY_TIMEOUT_MAX value on Windows #28672

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8 changes: 5 additions & 3 deletions Include/pythread.h
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Original file line number Diff line number Diff line change
Expand Up @@ -61,9 +61,11 @@ PyAPI_FUNC(int) _PyThread_at_fork_reinit(PyThread_type_lock *lock);
convert microseconds to nanoseconds. */
# define PY_TIMEOUT_MAX (LLONG_MAX / 1000)
#elif defined (NT_THREADS)
/* In the NT API, the timeout is a DWORD and is expressed in milliseconds */
# if 0xFFFFFFFFLL * 1000 < LLONG_MAX
# define PY_TIMEOUT_MAX (0xFFFFFFFFLL * 1000)
/* In the NT API, the timeout is a DWORD and is expressed in milliseconds,
* a positive number between 0 and 0x7FFFFFFF (see WaitForSingleObject()
* documentation). */
# if 0x7FFFFFFFLL * 1000 < LLONG_MAX
# define PY_TIMEOUT_MAX (0x7FFFFFFFLL * 1000)
# else
# define PY_TIMEOUT_MAX LLONG_MAX
# endif
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2021-09-30-08-57-50.bpo-41710.JMsPAW.rst
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@@ -0,0 +1,3 @@
Fix :data:`_thread.TIMEOUT_MAX` value on Windows: the maximum timeout is
0x7FFFFFFF milliseconds (around 24.9 days), not 0xFFFFFFFF milliseconds (around
49.7 days).
12 changes: 9 additions & 3 deletions Python/thread_nt.h
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Expand Up @@ -295,6 +295,10 @@ PyThread_free_lock(PyThread_type_lock aLock)
FreeNonRecursiveMutex(aLock) ;
}

// WaitForSingleObject() documentation: "The time-out value needs to be a
// positive number between 0 and 0x7FFFFFFF." INFINITE is equal to 0xFFFFFFFF.
const DWORD TIMEOUT_MS_MAX = 0x7FFFFFFF;

/*
* Return 1 on success if the lock was acquired
*
Expand All @@ -312,9 +316,11 @@ PyThread_acquire_lock_timed(PyThread_type_lock aLock,

if (microseconds >= 0) {
milliseconds = microseconds / 1000;
if (microseconds % 1000 > 0)
++milliseconds;
if (milliseconds > PY_DWORD_MAX) {
// Round milliseconds away from zero
if (microseconds % 1000 > 0) {
milliseconds++;
}
if (milliseconds > (PY_TIMEOUT_T)TIMEOUT_MS_MAX) {
Py_FatalError("Timeout larger than PY_TIMEOUT_MAX");
}
}
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