Re: [PATCH 3/5] ftrace perf: Use ftrace_ops::private to store event pointer

[Namhyung Kim <namhyung@kernel.org>]

On Wed, Mar 09, 2016 at 09:46:43PM +0100, Jiri Olsa wrote:
> Having following commands running concurrently:
> 
>   # perf record -e ftrace:function -a -o krava.data sleep 10
>   # perf record -e ftrace:function --filter 'ip == SyS_read' ls
> 
> will end up in the latter one to fail on the filter rules
> and store all functions (in perf.data) as instructed by the
> first perf record instead of just SyS_read records.
> 
> The reason for this is, that tracepoint code by default
> triggers all events that registered for the tracepoint.
> 
> While ftrace:function is special because ftrace_ops
> itself carries a filter and only the event that owns
> ftrace_ops is eligible to be triggered.
> 
> Fixing this by using ftrace_ops::private value to keep
> the perf_event pointer. This way we don't need to search
> for triggered event (as tracepoint handler does) and
> directly store sample.
> 
> Suggested-by: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung


> ---
>  include/linux/perf_event.h      |  3 +++
>  kernel/events/core.c            | 22 ++++++++++++++++++++++
>  kernel/trace/trace_event_perf.c | 10 +++-------
>  3 files changed, 28 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index a9d8cab18b00..a330dc06d90d 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -1008,6 +1008,9 @@ extern void perf_tp_event(u64 addr, u64 count, void *record,
>  			  int entry_size, struct pt_regs *regs,
>  			  struct hlist_head *head, int rctx,
>  			  struct task_struct *task);
> +void perf_function_event(struct perf_event *event,
> +			 void *record, int entry_size,
> +			 struct pt_regs *regs);
>  extern void perf_bp_event(struct perf_event *event, void *data);
>  
>  #ifndef perf_misc_flags
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index ca68fdcf47ce..18da90859c17 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -7063,6 +7063,28 @@ static void perf_event_free_bpf_prog(struct perf_event *event)
>  	}
>  }
>  
> +#ifdef CONFIG_FUNCTION_TRACER
> +void perf_function_event(struct perf_event *event,
> +			 void *record, int entry_size,
> +			 struct pt_regs *regs)
> +
> +{
> +	struct perf_sample_data data;
> +	struct perf_raw_record raw = {
> +		.size = entry_size,
> +		.data = record,
> +	};
> +
> +	if (event->hw.state & PERF_HES_STOPPED)
> +		return;
> +
> +	perf_sample_data_init(&data, 0, 0);
> +	data.raw = &raw;
> +
> +	perf_swevent_event(event, 1, &data, regs);
> +}
> +#endif /* CONFIG_FUNCTION_TRACER */
> +
>  #else
>  
>  static inline void perf_tp_register(void)
> diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
> index 0a3779bd18a1..087c811db04c 100644
> --- a/kernel/trace/trace_event_perf.c
> +++ b/kernel/trace/trace_event_perf.c
> @@ -328,14 +328,9 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
>  			  struct ftrace_ops *ops, struct pt_regs *pt_regs)
>  {
>  	struct ftrace_entry *entry;
> -	struct hlist_head *head;
>  	struct pt_regs regs;
>  	int rctx;
>  
> -	head = this_cpu_ptr(event_function.perf_events);
> -	if (hlist_empty(head))
> -		return;
> -
>  #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \
>  		    sizeof(u64)) - sizeof(u32))
>  
> @@ -349,8 +344,8 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
>  
>  	entry->ip = ip;
>  	entry->parent_ip = parent_ip;
> -	perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0,
> -			      1, &regs, head, NULL);
> +	perf_function_event(ops->private, entry, ENTRY_SIZE, &regs);
> +	perf_swevent_put_recursion_context(rctx);
>  
>  #undef ENTRY_SIZE
>  }
> @@ -359,6 +354,7 @@ static int perf_ftrace_function_register(struct perf_event *event)
>  {
>  	struct ftrace_ops *ops = &event->ftrace_ops;
>  
> +	ops->private = event;
>  	ops->flags |= FTRACE_OPS_FL_PER_CPU | FTRACE_OPS_FL_RCU;
>  	ops->func = perf_ftrace_function_call;
>  	return register_ftrace_function(ops);
> -- 
> 2.4.3
>