testing: `go -cover -race` finds race in coverage code @ tip

[lavalamp]

$ go version
go version devel +a1d74ad863fb Tue Sep 02 12:23:49 2014 -0700 linux/amd64

One sample race:

==================
WARNING: DATA RACE
Read by main goroutine:
  testing.coverReport()
      /home/travis/.gvm/gos/tip/src/pkg/testing/cover.go:89 +0x4f8
  testing.after()
      /home/travis/.gvm/gos/tip/src/pkg/testing/testing.go:596 +0x89d
  testing.Main()
      /home/travis/.gvm/gos/tip/src/pkg/testing/testing.go:450 +0x1e1
  main.main()
      github.com/GoogleCloudPlatform/kubernetes/pkg/proxy/config/_test/_testmain.go:117 +0x17a
Previous write by goroutine 11:
  sync/atomic.AddInt32()
      /home/travis/.gvm/gos/tip/src/pkg/runtime/race_amd64.s:255 +0xc
  github.com/GoogleCloudPlatform/kubernetes/pkg/proxy/config.handleServicesWatch()
      github.com/GoogleCloudPlatform/kubernetes/pkg/proxy/config/_test/_obj_test/api.go:93 +0x261
  github.com/GoogleCloudPlatform/kubernetes/pkg/proxy/config.(*SourceAPI).runServices()
      github.com/GoogleCloudPlatform/kubernetes/pkg/proxy/config/_test/_obj_test/api.go:71 +0x44b
  github.com/GoogleCloudPlatform/kubernetes/pkg/proxy/config.func·007()
      /home/travis/gopath/src/github.com/GoogleCloudPlatform/kubernetes/_output/go/src/github.com/GoogleCloudPlatform/kubernetes/pkg/proxy/config/api_test.go:39 +0x5e
Goroutine 11 (running) created at:
  github.com/GoogleCloudPlatform/kubernetes/pkg/proxy/config.TestServices()
      /home/travis/gopath/src/github.com/GoogleCloudPlatform/kubernetes/_output/go/src/github.com/GoogleCloudPlatform/kubernetes/pkg/proxy/config/api_test.go:40 +0x377
  testing.tRunner()
      /home/travis/.gvm/gos/tip/src/pkg/testing/testing.go:427 +0x112
==================

[bradfitz]

Comment 1:

Why are you filing a bug against Go instead of a bug against Kubernetes?

[bradfitz]

Comment 2:

Oh, you're saying the generated code from -cover has data races? Can you confirm that
there's no race when you run with -race and without -cover?

[lavalamp]

Comment 3:

Right, the coverage code has a race (or a false positive).
Yes, I can confirm that turning off coverage (and nothing else) causes the races to go
away: https://travis-ci.org/GoogleCloudPlatform/kubernetes/jobs/34241151

[adg]

Comment 4:

What if you set -covermode=atomic ?

[adg]

Comment 5:

Oh, I see from the stack trace that covermode _is_ set to atomic. (the write by
atomic.AddInt32 is the giveaway)

Labels changed: added release-go1.4.

Status changed to Accepted.

[dvyukov]

Comment 6:

Counters reading is not atomic. It must be.

Labels changed: added repo-main, threadsanitizer.

[gopherbot]

Comment 7:

CL https://golang.org/cl/141800043 mentions this issue.

[robpike]

Comment 8:

This issue was closed by revision d33ee0c.

Status changed to Fixed.