Re: [PATCH v15 09/12] perf record: Read from overwritable ring buffer

[Jiri Olsa]

On Tue, Jul 12, 2016 at 10:00:09AM +0000, Wang Nan wrote:

SBIP

> +		default:
> +			goto state_err;
> +		}
> +		break;
> +	}
> +	default:
> +		WARN_ONCE(1, "Shouldn't get there\n");
> +	}
> +
> +	rec->overwrite_evt_state = state;
> +
> +	switch (action) {
> +	case PAUSE:
> +		perf_evlist__pause(rec->evlist);
> +		break;
> +	case RESUME:
> +		perf_evlist__resume(rec->evlist);
> +		break;

so this is called on evlist with uninitialized backward_mmap,
which makes above calls fail, but luckily we dont check the
return values

I think we could set some evlist flag to know we have backward
mmaps and skip this function completely if we dont have any

thanks,
jirka