presto-main/src/main/java/io/prestosql/execution/resourcegroups/InternalResourceGroup.java/InternalResourceGroup/setHardConcurrencyLimit
class InternalResourceGroup:    @Managed
    @Override
    public void setHardConcurrencyLimit(int hardConcurrencyLimit)
    {
        checkArgument(hardConcurrencyLimit >= 0, "hardConcurrencyLimit is negative");
        synchronized (root) {
            boolean oldCanRun = canRunMore();
            this.hardConcurrencyLimit = hardConcurrencyLimit;
            if (canRunMore() != oldCanRun) {
                updateEligibility();
            }
        }
    }