golang/go

runtime: async preemption support on ARM64 breaks ARM64 on QEMU

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#36,981 opened on Feb 2, 2020

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Description

The change in 1b0b9809046c1862f8ea0240fe016e516c67676f breaks QEMU support for Go programs, resulting in a variety of crashes ranging from segmentation faults, illegal instructions and scheduler panics (holding locks).

This is partially recovered by the change in 73d20f8186a091c8d7e81b621136770981cf8e44 which prevents the crashes, but results in extremely poor performance; processes appear only able to use about 10-15% of a core compared to ~100% prior to 1b0b9809046c1862f8ea0240fe016e516c67676f.

What version of Go are you using (go version)?

Does this issue reproduce with the latest release?

No

What operating system and processor architecture are you using (go env)?

Natively on amd64/linux, but qemu-user with GOARCH=arm64.

What did you do?

In a checkout of gonum.org/v1/gonum/lapack/gonum, run GOARCH=arm64 go test -run Dgeev

I have tried to make a smaller reproducer, but have not managed yet.

What did you expect to see?

Other expected package failures.

What did you see instead?

A variety of crashes.

Contributor guide

Research direction
Investigate commit 1b0b9809046c1862f8ea0240fe016e516c67676f which introduced async preemption support for ARM64, and understand why it causes crashes on QEMU user mode. Focus on signal handling and memory model differences between QEMU and real hardware.
Tech stack
go
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GoGitARM64QEMU
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25