What steps will reproduce the problem?

func perpetuumMobile() {
  go perpetuumMobile()
}

func TestStopTheWorldDeadlock(t *testing.T) {
    runtime.GOMAXPROCS(3)
    compl := make(chan int, 1)
    go func() {
        for i := 0; i != 1000; i += 1 {
            runtime.GC()
        }
        compl <- 0
    }()
    go func() {
        for i := 0; i != 1000; i += 1 {
            runtime.GOMAXPROCS(3)
        }
    }()
    go perpetuumMobile();
    <- compl
}

What is the expected output?
Program does not deadlock.

What do you see instead?
Program deadlocks.

Which compiler are you using (5g, 6g, 8g, gccgo)?
6g

Which operating system are you using?
linux

Which revision are you using?  (hg identify)
6994a5f47fb9+ tip