linux-kernel - Re: [PATCH 6/6] perf parse events: demystify memory allocations

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Date:	Sun, 07 Jul 2013 10:45:13 -0600
From:	David Ahern <dsahern@...il.com>
To:	Jiri Olsa <jolsa@...hat.com>
CC:	acme@...stprotocols.net, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH 6/6] perf parse events: demystify memory allocations

On 7/7/13 9:26 AM, Jiri Olsa wrote:
> On Tue, Jul 02, 2013 at 01:27:25PM -0600, David Ahern wrote:
>> List heads are currently allocated way down the function chain in __add_event
>> and add_tracepoint and then freed when the scanner code calls
>> parse_events_update_lists.
>>
>> Be more explicit with where memory is allocated and who should free it. With
>> this patch the list_head is allocated in the scanner code and freed when the
>> scanner code calls parse_events_update_lists.
>>
>
> SNIP
>
>> @@ -266,9 +279,10 @@ event_legacy_mem:
>>   PE_PREFIX_MEM PE_VALUE ':' PE_MODIFIER_BP sep_dc
>>   {
>>   	struct parse_events_evlist *data = _data;
>> -	struct list_head *list = NULL;
>> +	struct list_head *list;
>>
>> -	ABORT_ON(parse_events_add_breakpoint(&list, &data->idx,
>> +	ALLOC_LIST(list);
>> +	ABORT_ON(parse_events_add_breakpoint(list, &data->idx,
>>   					     (void *) $2, $4));
>>   	$$ = list;
>>   }
>> @@ -276,9 +290,10 @@ PE_PREFIX_MEM PE_VALUE ':' PE_MODIFIER_BP sep_dc
>>   PE_PREFIX_MEM PE_VALUE sep_dc
>>   {
>>   	struct parse_events_evlist *data = _data;
>> -	struct list_head *list = NULL;
>> +	struct list_head *list;
>>
>> -	ABORT_ON(parse_events_add_breakpoint(&list, &data->idx,
>> +	ALLOC_LIST(list);
>> +	ABORT_ON(parse_events_add_breakpoint(list, &data->idx,
>>   					     (void *) $2, NULL));
>
> so who now frees the list if there's an error
> in parse_events_add_breakpoint?

According to valgrind that memory is not freed prior to this patch, so 
this one does not introduce new leaks.

>
> ditto for other ABORT_ON cases

I will whip up a patch to free memory on failure paths.

David

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