Re: [PATCH v1 1/5] perf: add context parameter to perf_event overflow handler

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

On Wed, 2011-05-11 at 11:55 -0400, Avi Kivity wrote:
> +++ b/include/linux/perf_event.h
> @@ -709,7 +709,9 @@ struct perf_buffer {
>  
>  struct perf_sample_data;
>  
> -typedef void (*perf_overflow_handler_t)(struct perf_event *, int,
> +typedef void (*perf_overflow_handler_t)(void *context,
> +                                       struct perf_event *event,
> +                                       int,
>                                         struct perf_sample_data *,
>                                         struct pt_regs *regs);
>  
> @@ -855,6 +857,7 @@ struct perf_event {
>         u64                             id;
>  
>         perf_overflow_handler_t         overflow_handler;
> +       void                            *overflow_handler_context;
>  
>  #ifdef CONFIG_EVENT_TRACING
>         struct ftrace_event_call        *tp_event; 

If you're adding a pointer here, then why pass it along in the callback
thing if it already has the perf_event *?

It seems to me the callback can easily do
event->overflow_handler_context if it needs the thing.