In my open source file descriptor leak checker (Linux only) for Gomega,
Go's race detector flags a race condition in my code where I need to check
whether a Cmd.Process already has terminated
<https://github.com/thediveo/fdooze/blob/05aae68770fd287e51aea8dd55ff336164cb3f49/session/session_fds.go#L21>
as its ProcessState has been set.
if session.Command.ProcessState != nil {
return nil, errors.New("session has already ended")
}
Now, this check might be called be called from a different Goroutine than
another Goroutine waiting for the command to exit. In particular, this is
the (what I consider to be the relevant) output of the race detector:
WARNING: DATA RACE
Write at 0x00c0002e8208 by goroutine 16:
os/exec.(*Cmd).Wait()
/home/.../sdk/go1.19rc2/src/os/exec/exec.go:598 +0x1eb
github.com/onsi/gomega/gexec.(*Session).monitorForExit()
/home/.../go/pkg/mod/github.com/onsi/gomega@v1.20.0/gexec/session.go:197
+0x44
github.com/onsi/gomega/gexec.Start.func1()
/home/.../go/pkg/mod/github.com/onsi/gomega@v1.20.0/gexec/session.go:96
+0x47
Previous read at 0x00c0002e8208 by goroutine 12:
github.com/thediveo/fdooze/session.FiledescriptorsFor()
/home/.../github/fdooze/session/session_fds.go:21 +0x1b7
github.com/thediveo/fdooze/session.glob..func1.1.1()
/home/.../github/fdooze/session/session_fds_test.go:45 +0x30
runtime.call16()
/home/.../sdk/go1.19rc2/src/runtime/asm_amd64.s:724 +0x48
reflect.Value.Call()
/home/.../sdk/go1.19rc2/src/reflect/value.go:368 +0xc7
github.com/onsi/gomega/internal.NewAsyncAssertion.func1()
/home/.../go/pkg/mod/github.com/onsi/gomega@v1.20.0/internal/async_assertion.go:48
+0x16e
github.com/onsi/gomega/internal.(*AsyncAssertion).pollActual()
/home/.../go/pkg/mod/github.com/onsi/gomega@v1.20.0/internal/async_assertion.go:132
+0x82
github.com/onsi/gomega/internal.(*AsyncAssertion).match()
/home/.../go/pkg/mod/github.com/onsi/gomega@v1.20.0/internal/async_assertion.go:162
+0xe4
github.com/onsi/gomega/internal.(*AsyncAssertion).ShouldNot()
/home/.../go/pkg/mod/github.com/onsi/gomega@v1.20.0/internal/async_assertion.go:112
+0xa9
github.com/thediveo/fdooze/session.glob..func1.1()
/home/.../github/fdooze/session/session_fds_test.go:65 +0xf41
github.com/onsi/ginkgo/v2/internal.(*Suite).runNode.func2()
/home/.../go/pkg/mod/github.com/onsi/ginkgo/v2@v2.1.4/internal/suite.go:596
+0xea
Is there actually any way to check use Cmd.ProcessState at all from a
thread different from the one doing a Cmd.Wait? Might this be a design
"weakness" of the Cmd type in that it doesn't cover such use cases?
Any idea for a work around to find if the command might already have
(prematurely) finished by the time I try to check for its open file
descriptors?
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