[PATCH] perf: fix missing event name init for default event

[PATCH] perf: fix missing event name init for default event

[Stephane Eranian]

When no event is given to perf record, perf top, a default
event is initialized (cycles). However, perf_evlist__add_default()
was not setting the symbolic name for the event. Perf top
worked simply because it was reconstructing the name from the event
code. But it should not have to do this. This patch initializes the
evsel->name field properly.

Signed-off-by: Stephane Eranian <eranian@google.com>
---

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index b021ea9..1584af6 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -87,6 +87,13 @@ int perf_evlist__add_default(struct perf_evlist *evlist)
 	if (evsel == NULL)
 		return -ENOMEM;
 
+	/* use strdup() because free(evsel) assumes name is allocated */
+	evsel->name = strdup("cycles");
+	if (!evsel->name) {
+		free(evsel);
+		return -ENOMEM;
+	}
+
 	perf_evlist__add(evlist, evsel);
 	return 0;
 }

Re: [PATCH] perf: fix missing event name init for default event

[Ingo Molnar]

* Stephane Eranian <eranian@google.com> wrote:

> @@ -87,6 +87,13 @@ int perf_evlist__add_default(struct perf_evlist *evlist)
>  	if (evsel == NULL)
>  		return -ENOMEM;
>  
> +	/* use strdup() because free(evsel) assumes name is allocated */
> +	evsel->name = strdup("cycles");
> +	if (!evsel->name) {
> +		free(evsel);
> +		return -ENOMEM;
> +	}
> +
>  	perf_evlist__add(evlist, evsel);
>  	return 0;
>  }

Hm, nice fix, but this function should really follow the standard 
exception tear-down sequence pattern we use in the kernel:

  	if (evsel == NULL)
		goto err;

	...

	if (!evsel->name)
		goto err_free;

	...

	return 0;

err_free:
	free(evsel);
err:
	return -ENOMEM;

Thanks,

	Ingo

Re: [PATCH] perf: fix missing event name init for default event

[Stephane Eranian]

On Mon, Jun 6, 2011 at 7:32 PM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Stephane Eranian <eranian@google.com> wrote:
>
>> @@ -87,6 +87,13 @@ int perf_evlist__add_default(struct perf_evlist *evlist)
>>       if (evsel == NULL)
>>               return -ENOMEM;
>>
>> +     /* use strdup() because free(evsel) assumes name is allocated */
>> +     evsel->name = strdup("cycles");
>> +     if (!evsel->name) {
>> +             free(evsel);
>> +             return -ENOMEM;
>> +     }
>> +
>>       perf_evlist__add(evlist, evsel);
>>       return 0;
>>  }
>
> Hm, nice fix, but this function should really follow the standard
> exception tear-down sequence pattern we use in the kernel:
>
Fine, I can respin that patch.

>        if (evsel == NULL)
>                goto err;
>
>        ...
>
>        if (!evsel->name)
>                goto err_free;
>
>        ...
>
>        return 0;
>
> err_free:
>        free(evsel);
> err:
>        return -ENOMEM;
>
> Thanks,
>
>        Ingo
>