On Sun, Oct 20, 2019 at 10:51:56AM -0700, Andi Kleen wrote:

SNIP

> @@ -92,8 +93,12 @@ static int pmu_format(const char *name, struct list_head 
> *format)
>       snprintf(path, PATH_MAX,
>                "%s" EVENT_SOURCE_DEVICE_PATH "%s/format", sysfs, name);
>  
> -     if (stat(path, &st) < 0)
> +     if (lookup_fncache(path, &res) && !res)
> +             return 0;
> +
> +     if (!res && access(path, R_OK) < 0)
>               return 0;       /* no error if format does not exist */
> +     update_fncache(path, true);
>  
>       if (perf_pmu__format_parse(path, format))
>               return -1;
> @@ -470,9 +475,9 @@ static int pmu_aliases_parse(char *dir, struct list_head 
> *head)
>   */
>  static int pmu_aliases(const char *name, struct list_head *head)
>  {
> -     struct stat st;
>       char path[PATH_MAX];
>       const char *sysfs = sysfs__mountpoint();
> +     bool res = false;
>  
>       if (!sysfs)
>               return -1;
> @@ -480,8 +485,11 @@ static int pmu_aliases(const char *name, struct 
> list_head *head)
>       snprintf(path, PATH_MAX,
>                "%s/bus/event_source/devices/%s/events", sysfs, name);
>  
> -     if (stat(path, &st) < 0)
> -             return 0;        /* no error if 'events' does not exist */
> +     if (lookup_fncache(path, &res) && !res)
> +             return 0;
> +     if (!res && access(path, R_OK) < 0)
> +             return 0;
> +     update_fncache(path, true);

I was thinking that maybe you dont need to have the fncache::res,
but then I realized we have 2 kind of information in here:
  - we processed this file
  - is present file present

so I think you should update the result on each update_fncache call,
not only when it's succesful


also, could you please make single function API for this?
sonething like:

  is_the_file_there(path)

that would encapsulate those calls

thanks,
jirka

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