runtime/race: runaway memory consumption

[dvyukov]

The following benchmark consumes unlimited amount of memory:

func BenchmarkSyncLeak(b *testing.B) {
    const (
        G = 1000
        S = 1000
        H = 10
    )
    var wg sync.WaitGroup
    wg.Add(G)
    for g := 0; g < G; g++ {
        go func() {
            defer wg.Done()
            hold := make([][]uint32, H)
            for i := 0; i < b.N; i++ {
                a := make([]uint32, S)
                atomic.AddUint32(&a[rand.Intn(len(a))], 1)
                hold[rand.Intn(len(hold))] = a
            }
            _ = hold
        }()
    }
    wg.Wait()
}

The main cause is that race runtime does not wipe stale synchronization objects from heap memory blocks.

[gopherbot]

CL https://golang.org/cl/19970 mentions this issue.