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x/sync/singleflight: runtime.Goexit blocks waiting channels forever #67087

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abursavich opened this issue Apr 27, 2024 · 1 comment
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x/sync/singleflight: runtime.Goexit blocks waiting channels forever #67087

abursavich opened this issue Apr 27, 2024 · 1 comment
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Unreleased

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@abursavich
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abursavich commented Apr 27, 2024 •
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Go version

go version go1.22.2 darwin/arm64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='arm64'
GOBIN=''
GOCACHE='/Users/amb/Library/Caches/go-build'
GOENV='/Users/amb/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/amb/go/pkg/mod'
GONOPROXY='github.com/REDACTED/*'
GONOSUMDB='github.com/REDACTED/*'
GOOS='darwin'
GOPATH='/Users/amb/go'
GOPRIVATE='github.com/REDACTED/*'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.22.2'
GCCGO='gccgo'
AR='ar'
CC='clang'
CXX='clang++'
CGO_ENABLED='1'
GOMOD='/Users/amb/src/singleflight/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/p4/t2ydl1qj10s99sfykmbnp6cc0000gq/T/go-build239865489=/tmp/go-build -gno-record-gcc-switches -fno-common'

What did you do?

Example with panic: https://go.dev/play/p/fKxw87DNRY6
Example with runtime.Goexit: https://go.dev/play/p/PJIOUMA4eTc

What did you see happen?

I'm forking singleflight to add contexts and generics and noticed an inconsistent behavior. You may or may not consider it a bug.

The package goes out of its way to make panics unrecoverable when using DoChan specifically so that any waiting channels won't be blocked forever. The package also goes out of its way to handle runtime.Goexit when using Do but it does nothing to unblock DoChan channels that are waiting when this happens.

What did you expect to see?

I don't have a strong opinion about what the right thing to do is here. I might suggest closing the channels without sending a result, but it's specifically documented that the channel won't be closed. I'm leaning toward sending the errGoexit error to those channels, but I'm not really happy with that either.
@gopherbot gopherbot added this to the Unreleased milestone Apr 27, 2024
@seankhliao
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Duplicate of #52557

@seankhliao seankhliao marked this as a duplicate of #52557 Apr 27, 2024
@seankhliao seankhliao closed this as not planned Won't fix, can't repro, duplicate, stale Apr 27, 2024
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@abursavich @gopherbot @seankhliao