runtime: async preemption support on ARM64 breaks ARM64 on QEMU #36981
Open
Description
The change in 1b0b980 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 73d20f8 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 1b0b980.
What version of Go are you using (go version)?
$ go version go version devel +1b0b980904 Thu Nov 7 19:18:12 2019 +0000 linux/amd64
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.
go env Output
$ go env GO111MODULE="on" GOARCH="arm64" GOBIN="/home/user/bin" GOCACHE="/home/user/.cache/go-build" GOENV="/home/user/.config/go/env" GOEXE="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="linux" GONOPROXY="" GONOSUMDB="" GOOS="linux" GOPATH="/home/user" GOPRIVATE="" GOPROXY="https://proxy.golang.org,direct" GOROOT="/home/user/go" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/home/user/go/pkg/tool/linux_amd64" GCCGO="gccgo" AR="ar" CC="gcc" CXX="g++" CGO_ENABLED="0" GOMOD="/dev/null" CGO_CFLAGS="-g -O2" CGO_CPPFLAGS="" CGO_CXXFLAGS="-g -O2" CGO_FFLAGS="-g -O2" CGO_LDFLAGS="-g -O2" PKG_CONFIG="pkg-config" GOGCCFLAGS="-fPIC -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build167327579=/tmp/go-build -gno-record-gcc-switches" ~ $ lsb_release -d Description: Ubuntu 18.04.3 LTS ~ $ dpkg -l qemu-user qemu-system-common qemu-system-arm Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad) ||/ Name Version Architecture Description +++-=============================-===================-===================-=============================================================== ii qemu-system-arm 1:2.11+dfsg-1ubuntu amd64 QEMU full system emulation binaries (arm) ii qemu-system-common 1:2.11+dfsg-1ubuntu amd64 QEMU full system emulation binaries (common files) ii qemu-user 1:2.11+dfsg-1ubuntu amd64 QEMU user mode emulation binaries
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.