Re: [PATCH v3 08/10] cxl: add an optional pid check to event parsing

[Steven Rostedt <rostedt@goodmis.org>]

On Wed, 02 Nov 2022 14:20:49 -0700
Dave Jiang <dave.jiang@intel.com> wrote:

> From: Alison Schofield <alison.schofield@intel.com>
> 
> When parsing CXL events, callers may only be interested in events
> that originate from the current process. Introduce an optional
> argument to the event trace context: event_pid. When event_pid is
> present, only include events with a matching pid in the returned
> JSON list. It is not a failure to see other, non matching results.
> Simply skip those.
> 
> The initial use case for this is the listing of media errors,
> where only the media-errors requested by this process are wanted.
> 
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  cxl/event_trace.c |   18 ++++++++++++++++++
>  cxl/event_trace.h |    1 +
>  2 files changed, 19 insertions(+)
> 
> diff --git a/cxl/event_trace.c b/cxl/event_trace.c
> index bcd4f8b2968e..0be6317e6ada 100644
> --- a/cxl/event_trace.c
> +++ b/cxl/event_trace.c
> @@ -166,6 +166,19 @@ err_jevent:
>  	return rc;
>  }
>  
> +static bool cxl_match_pid(struct tep_event *event, struct tep_record *record,
> +			  int pid)
> +{
> +	unsigned long long val;
> +
> +	if (tep_get_common_field_val(NULL, event, "common_pid", record, &val, 0))

There's also a way to get the pid directly:

   pid = tep_data_pid(tep, record);

-- Steve

> +		return false;
> +	if (pid != (int)val)
> +		return false;
> +
> +	return true;
> +}
> +
>  static int cxl_event_parse_cb(struct tep_event *event, struct tep_record *record,
>  		int cpu, void *ctx)
>  {
> @@ -180,6 +193,11 @@ static int cxl_event_parse_cb(struct tep_event *event, struct tep_record *record
>  			return 0;
>  	}
>  
> +	if (event_ctx->event_pid) {
> +		if (!cxl_match_pid(event, record, event_ctx->event_pid))
> +			return 0;
> +	}
> +
>  	if (event_ctx->parse_event)
>  		return event_ctx->parse_event(event, record, &event_ctx->jlist_head);
>  
> diff --git a/cxl/event_trace.h b/cxl/event_trace.h
> index 17d922f922c1..64f07854b91b 100644
> --- a/cxl/event_trace.h
> +++ b/cxl/event_trace.h
> @@ -15,6 +15,7 @@ struct event_ctx {
>  	const char *system;
>  	struct list_head jlist_head;
>  	const char *event_name;					/* optional */
> +	int event_pid;						/* optional */
>  	int (*parse_event)(struct tep_event *event, struct tep_record *record,
>  			   struct list_head *jlist_head);	/* optional */
>  };
>