On Fri, Dec 11, 2015 at 03:36:36PM +0200, Alexander Shishkin wrote:
> +static int
> +perf_event_set_itrace_filter(struct perf_event *event, char *filter_str)
> +{
> + int ret = 0;
> +
> + /*
> + * Since this is called in perf_ioctl() path, we're already holding
> + * ctx::mutex.
> + */
> + lockdep_assert_held(&event->ctx->mutex);
> +
> + /*
> + * For now, we only support filtering in per-task events; doing so
> + * for cpu-wide events requires additional context switching trickery,
> + * since same object code will be mapped at different virtual
> + * addresses in different processes.
> + */
> + if (!event->ctx->task)
> + return -EOPNOTSUPP;
> +
> + /* remove existing filters, if any */
> + perf_itrace_filters_clear(event);
> +
> + ret = perf_event_parse_itrace_filter(event, filter_str);
> + if (!ret) {
> + perf_itrace_filters_apply(event);
> +
> + ret = perf_event_itrace_filters_setup(event);
> + if (ret)
> + perf_itrace_filters_clear(event);
This is what I meant, if you try and set a 'wrong' filter while it
already has filters set, you'll not only error out, you'll also wipe the
current state.
This seems wrong.
> + }
> +
> + return ret;
> +}
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