Re: [PATCH] tracing/filters: add filter_mutex to protect filter predicates

[Li Zefan <lizf@cn.fujitsu.com>]

Tom Zanussi wrote:
> This patch adds a filter_mutex to prevent the filter predicates from
> being accessed concurrently by various external functions.
> 
> It's based on a previous patch by Li Zefan:
>         "[PATCH 7/7] tracing/filters: make filter preds RCU safe"
> 
> but any problems with it were added by me. ;-)
> 
> Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
> 

Reviewed-and-tested-by: Li Zefan <lizf@cn.fujitsu.com>

except:

> @@ -348,17 +399,15 @@ int filter_add_subsystem_pred(struct event_subsystem *system,
>  		if (strcmp(call->system, system->name))
>  			continue;
>  
> -		if (!find_event_field(call, pred->field_name))
> -			continue;
> -
> -		err = filter_add_pred(call, pred);
> +		err = __filter_add_pred(call, pred);
>  		if (err == -ENOMEM) {
>  			system->preds[system->n_preds] = NULL;
> -			return err;
> +			system->n_preds--;
> +			break;

now we return 0 but not ENOMEM in this failure case.

>  		}
>  	}
>  
> -	system->n_preds++;
> +	mutex_unlock(&filter_mutex);
>  
>  	return 0;
>  }