linux-kernel - Re: [PATCH 01/13] perf: Simplify perf_event

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Date:   Fri, 3 Nov 2023 13:38:05 +0100
From:   Jiri Olsa <olsajiri@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...nel.org, linux-kernel@...r.kernel.org, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        namhyung@...nel.org, irogers@...gle.com, adrian.hunter@...el.com
Subject: Re: [PATCH 01/13] perf: Simplify perf_event_alloc() error path

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);
>  }
>  
> 
>