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runtime/race: TestRaceRange is not always detected as a race #10589

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rsc opened this issue Apr 27, 2015 · 5 comments
Closed

runtime/race: TestRaceRange is not always detected as a race #10589

rsc opened this issue Apr 27, 2015 · 5 comments
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Go1.6

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@rsc
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rsc commented Apr 27, 2015

It seems to me that TestRaceRange should always be detected as a race. The code is:

func TestRaceRange(t *testing.T) {
    const N = 2
    var a [N]int
    var x, y int
    done := make(chan bool, N)
    for i, v := range a {
        go func(i int) {
            // we don't want a write-vs-write race
            // so there is no array b here
            if i == 0 {
                x = v
            } else {
                y = v
            }
            done <- true
        }(i)
    }
    for i := 0; i < N; i++ {
        <-done
    }
}

The actual execution is

v = a[0]
go func() { x = v }()
v = a[1]
go func() { y = v }()

and the race is between the x = v and the v = a[1].

When Austin tweaked the goroutine scheduler behavior, the race detector stopped detecting this race. Adding a Gosched brought the detection of the race back, but it seems like it should be detected even without a Gosched.

@aclements
@rsc rsc added this to the Go1.5 milestone Apr 27, 2015
@dvyukov
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dvyukov commented Apr 28, 2015

This is a bug in race runtime. Fixed upstream:
http://llvm.org/viewvc/llvm-project?view=revision&revision=236008
Need to update race runtime, which is difficult until #8653 is resolved.

@aclements
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@dvyukov, it looks like #8653 is unresolved and has milestone Unreleased. Should we bump this issue to Unreleased?

@rsc rsc modified the milestones: Unplanned, Go1.5 Jul 15, 2015
@dvyukov dvyukov modified the milestones: Go1.6, Unplanned Jul 19, 2015
@rsc
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rsc commented Nov 5, 2015

It would be nice to bring in a new copy of the race runtime for Go 1.6, whether or not #8653 is fixed.

@dvyukov
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dvyukov commented Nov 5, 2015

We need to resolve #8653. The project will benefit is not only me can rebuild the runtime. And even for me it is painful currently. I don't access to any windows nor darwin machines after the move.
Do we have all 4 OSes in the new infrastructure?
@bradfitz can you help me with this? I can work out the scripts, but there were issues like something is missing on the machines, or unclear how to do something.

@bradfitz
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I can answer concrete questions about the build system & gomote, but not "why doesn't the race detector build with gomote?".

@golang golang locked and limited conversation to collaborators Nov 16, 2016
@rsc rsc unassigned dvyukov Jun 23, 2022
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