From ac645eaa0efc982eb238188a5f14835d2c1f8d18 Mon Sep 17 00:00:00 2001 From: Rhys Hiltner Date: Thu, 8 May 2025 10:59:18 -0700 Subject: [PATCH] runtime: avoid overflow in mutex delay calculation If cputicks is in the top quarter of the int64's range, adding two values together will overflow and confuse the subsequent calculations, leading to zero-duration contention events in the profile. This fixes the TestRuntimeLockMetricsAndProfile failures on the linux-s390x builder. Change-Id: Icb814c39a8702379dfd71c06a53b2618e3589e07 Reviewed-on: https://go-review.googlesource.com/c/go/+/671115 Reviewed-by: Michael Knyszek TryBot-Result: Gopher Robot Run-TryBot: Rhys Hiltner LUCI-TryBot-Result: Go LUCI Auto-Submit: Michael Knyszek Reviewed-by: Cherry Mui --- src/runtime/lock_spinbit.go | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/runtime/lock_spinbit.go b/src/runtime/lock_spinbit.go index c2a6c76629..f90698a4c9 100644 --- a/src/runtime/lock_spinbit.go +++ b/src/runtime/lock_spinbit.go @@ -404,7 +404,7 @@ useStackLock: n++ next := node.mWaitList.next.ptr() if next == nil { - cycles := endTicks - (head.mWaitList.startTicks+node.mWaitList.startTicks)/2 + cycles := ((endTicks - head.mWaitList.startTicks) + (endTicks - node.mWaitList.startTicks)) / 2 node.mWaitList.startTicks = endTicks head.mWaitList.startTicks = endTicks getg().m.mLockProfile.recordUnlock(cycles * int64(n)) -- 2.51.0