From 2a1a0186d1a099dc94c28090b77603c3c17e0bda Mon Sep 17 00:00:00 2001 From: bobince Date: Wed, 11 Mar 2020 23:39:02 +0000 Subject: [PATCH] bpo-39847: EnterNonRecursiveMutex() uses GetTickCount64() (GH-18780) The 32-bit (49-day) TickCount relied on in EnterNonRecursiveMutex can overflow in the gap between the 'target' time and the 'now' time WaitForSingleObjectEx returns, causing the loop to think it needs to wait another 49 days. This is most likely to happen when the machine is hibernated during WaitForSingleObjectEx. This makes acquiring a lock/event/etc from the _thread or threading module appear to never timeout. Replace with GetTickCount64 - this is OK now Python no longer supports XP which lacks it, and is in use for time.monotonic(). Co-authored-by: And Clover (cherry picked from commit 64838ce7172c7a92183b39b22504b433a33a884d) Co-authored-by: bobince --- .../next/Windows/2020-03-04-17-05-11.bpo-39847.C3N2m3.rst | 2 ++ Python/thread_nt.h | 6 +++--- 2 files changed, 5 insertions(+), 3 deletions(-) create mode 100644 Misc/NEWS.d/next/Windows/2020-03-04-17-05-11.bpo-39847.C3N2m3.rst diff --git a/Misc/NEWS.d/next/Windows/2020-03-04-17-05-11.bpo-39847.C3N2m3.rst b/Misc/NEWS.d/next/Windows/2020-03-04-17-05-11.bpo-39847.C3N2m3.rst new file mode 100644 index 00000000000000..acfbce53eb3997 --- /dev/null +++ b/Misc/NEWS.d/next/Windows/2020-03-04-17-05-11.bpo-39847.C3N2m3.rst @@ -0,0 +1,2 @@ +Avoid hang when computer is hibernated whilst waiting for a mutex (for +lock-related objects from :mod:`threading`) around 49-day uptime. diff --git a/Python/thread_nt.h b/Python/thread_nt.h index a5246dd0504dbb..23d585cf9fa6c0 100644 --- a/Python/thread_nt.h +++ b/Python/thread_nt.h @@ -75,16 +75,16 @@ EnterNonRecursiveMutex(PNRMUTEX mutex, DWORD milliseconds) } } else if (milliseconds != 0) { /* wait at least until the target */ - DWORD now, target = GetTickCount() + milliseconds; + ULONGLONG now, target = GetTickCount64() + milliseconds; while (mutex->locked) { if (PyCOND_TIMEDWAIT(&mutex->cv, &mutex->cs, (long long)milliseconds*1000) < 0) { result = WAIT_FAILED; break; } - now = GetTickCount(); + now = GetTickCount64(); if (target <= now) break; - milliseconds = target-now; + milliseconds = (DWORD)(target-now); } } if (!mutex->locked) {