linux-kernel - Re: [PATCH 01/10] perf, tools: Dont stop PMU parsing on alias parse error

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Date:	Mon, 21 Dec 2015 17:08:57 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	acme@...nel.org, peterz@...radead.org, jolsa@...nel.org,
	mingo@...nel.org, linux-kernel@...r.kernel.org, eranian@...gle.com,
	namhyung@...nel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 01/10] perf, tools: Dont stop PMU parsing on alias parse
 error

On Tue, Dec 15, 2015 at 04:54:17PM -0800, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> When an error happens during alias parsing currently the complete
> parsing of all attributes of the PMU is stopped. This is breaks
> old perf on a newer kernel that may have not-yet-know
> alias attributes (such as .scale or .per-pkg).

I kind of recall seeing similar patch, but looks like
it never made it in

> 
> Continue when some attribute is unparseable.
> 
> This is IMHO a stable candidate and should be backported
> to older versions to avoid problems with newer kernels.
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> ---
>  tools/perf/util/pmu.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index e4b173d..8a520e9 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -283,13 +283,12 @@ static int pmu_aliases_parse(char *dir, struct list_head *head)
>  {
>  	struct dirent *evt_ent;
>  	DIR *event_dir;
> -	int ret = 0;
>  
>  	event_dir = opendir(dir);
>  	if (!event_dir)
>  		return -EINVAL;
>  
> -	while (!ret && (evt_ent = readdir(event_dir))) {
> +	while ((evt_ent = readdir(event_dir))) {
>  		char path[PATH_MAX];
>  		char *name = evt_ent->d_name;
>  		FILE *file;
> @@ -305,17 +304,16 @@ static int pmu_aliases_parse(char *dir, struct list_head *head)
>  
>  		snprintf(path, PATH_MAX, "%s/%s", dir, name);
>  
> -		ret = -EINVAL;
>  		file = fopen(path, "r");
>  		if (!file)
> -			break;
> +			continue;

I think we should emit warning in case of failure to let user know 

>  
> -		ret = perf_pmu__new_alias(head, dir, name, file);

same here

> +		perf_pmu__new_alias(head, dir, name, file);
>  		fclose(file);
>  	}
>  

thanks,
jirka
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