time, runtime: scheduled timer may never fire if GOMAXPROCS is reduced [1.15 backport]

[gopherbot]

@ianlancetaylor requested issue #45716 to be considered for backport to the next 1.15 minor release.

@gopherbot Please open backport to 1.15 branch.

[ianlancetaylor]

This was already fixed on the 1.16 branch by CL 300610. This issue is to backport that CL to the 1.15 branch as well.

[gopherbot]

Change https://golang.org/cl/313130 mentions this issue: [release-branch.go1.15] runtime, time: disable preemption in addtimer

[gopherbot]

Change https://golang.org/cl/313129 mentions this issue: [release-branch.go1.15] runtime, time: disable preemption in addtimer

[toothrot]

Approved. This is a serious issue with no workaround.

[gopherbot]

Closed by merging 72ccabc to release-branch.go1.15.