Re: [PATCH 01/13] perf: Simplify perf_event_alloc() error path

Jiri Olsa
2023-11-03T12:38:14Z

On Thu, Nov 02, 2023 at 04:09:20PM +0100, Peter Zijlstra wrote:

SNIP

> @@ -11936,24 +11957,24 @@ perf_event_alloc(struct perf_event_attr
> */
> if (pmu->task_ctx_nr == perf_invalid_context && (task || cgroup_fd != -1)) {
> err = -EINVAL;
> - goto err_pmu;
> + goto err;
> }
>
> if (event->attr.aux_output &&
> !(pmu->capabilities & PERF_PMU_CAP_AUX_OUTPUT)) {
> err = -EOPNOTSUPP;
> - goto err_pmu;
> + goto err;
> }
>
> if (cgroup_fd != -1) {
> err = perf_cgroup_connect(cgroup_fd, event, attr, group_leader);
> if (err)
> - goto err_pmu;
> + goto err;
> }
>
> err = exclusive_event_init(event);
> if (err)
> - goto err_pmu;
> + goto err;
>
> if (has_addr_filter(event)) {
> event->addr_filter_ranges = kcalloc(pmu->nr_addr_filters,
> @@ -11961,7 +11982,7 @@ perf_event_alloc(struct perf_event_attr
> GFP_KERNEL);
> if (!event->addr_filter_ranges) {
> err = -ENOMEM;
> - goto err_per_task;
> + goto err;
> }
>
> /*
> @@ -11986,41 +12007,21 @@ perf_event_alloc(struct perf_event_attr
> if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) {
> err = get_callchain_buffers(attr->sample_max_stack);
> if (err)
> - goto err_addr_filters;
> + goto err;
> }
> }
>
> err = security_perf_event_alloc(event);
> if (err)
> - goto err_callchain_buffer;
> + goto err;
>
> /* symmetric to unaccount_event() in _free_event() */
> account_event(event);
>
> return event;
>
> -err_callchain_buffer:
> - if (!event->parent) {
> - if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
> - put_callchain_buffers();
> - }

hum, so this is now called all the time via __free_event, but it should
be called only if we passed get_callchain_buffers call.. this could screw
up nr_callchain_events number eventually no?

jirka

> -err_addr_filters:
> - kfree(event->addr_filter_ranges);
> -
> -err_per_task:
> - exclusive_event_destroy(event);
> -
> -err_pmu:
> - if (is_cgroup_event(event))
> - perf_detach_cgroup(event);
> - if (event->destroy)
> - event->destroy(event);
> - module_put(pmu->module);
> -err_ns:
> - if (event->hw.target)
> - put_task_struct(event->hw.target);
> - call_rcu(&event->rcu_head, free_event_rcu);
> -
> +err:
> + __free_event(event);
> return ERR_PTR(err);
> }
>
>
>