[DTrace-devel] [PATCH 01/13] Change use of dtrace_probe_iter()

[Kris Van Hees]

On Wed, Jul 01, 2020 at 10:41:06PM -0400, eugene.loh at oracle.com wrote:
> From: Eugene Loh <eugene.loh at oracle.com>
> 
> In DTrace v1, dtrace_probe_iter() was used to iterate over probes,
> using dt_probe_iter() as a callback function.
> 
> In the current release, dtrace_probe_iter() will be used as an external
> API, with dt_probe_iter() the "internal" (to libdtrace) interface.
> 
> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
> ---
>  libdtrace/dt_probe.c | 26 +++++++++-----------------
>  1 file changed, 9 insertions(+), 17 deletions(-)
> 
> diff --git a/libdtrace/dt_probe.c b/libdtrace/dt_probe.c
> index b6c79354..46c47fbe 100644
> --- a/libdtrace/dt_probe.c
> +++ b/libdtrace/dt_probe.c
> @@ -960,10 +960,10 @@ dt_probe_args_info(dtrace_hdl_t *dtp, dt_probe_t *prp)
>  
>  /*ARGSUSED*/
>  static int
> -dt_probe_desc(dtrace_hdl_t *dtp, const dtrace_probedesc_t *pdp, void *arg)
> +dt_probe_representative(dtrace_hdl_t *dtp, const dt_probe_t *prp, void *arg)

I think dt_probe_first_match would be a more appropriate name since that is
what this callback provides.  Also, change the last arg type to be dt_probe_t **
so you dont't have to do the cast twice below.

>  {
> -	if (((dtrace_probedesc_t *)arg)->id == DTRACE_IDNONE) {
> -		memcpy(arg, pdp, sizeof (dtrace_probedesc_t));
> +	if (*((dt_probe_t **)arg) == NULL) {
> +		*((dt_probe_t **)arg) = prp;

See above concerning the type of arg and avoiding the casts..

>  		return (0);
>  	}
>  
> @@ -982,24 +982,20 @@ dt_probe_info(dtrace_hdl_t *dtp, const dtrace_probedesc_t *pdp,
>  	dt_probe_t *prp = NULL;
>  	const dtrace_pattr_t *pap;
>  	dt_provider_t *pvp;
> -	dtrace_probedesc_t pd;
>  	int m;
>  
> -	memset(&pd, 0, sizeof (pd));
> -	pd.id = DTRACE_IDNONE;
> -
>  	/*
> -	 * Call dtrace_probe_iter() to find matching probes.  Our
> +	 * Call dt_probe_iter() to find matching probes.  Our
>  	 * dt_probe_desc() callback will produce the following results:
>  	 *
> -	 * m < 0 dtrace_probe_iter() found zero matches (or failed).
> -	 * m > 0 dtrace_probe_iter() found more than one match.
> -	 * m = 0 dtrace_probe_iter() found exactly one match.
> +	 * m < 0 dt_probe_iter() found zero matches (or failed).
> +	 * m > 0 dt_probe_iter() found more than one match.
> +	 * m = 0 dt_probe_iter() found exactly one match.
>  	 */

The comment block needs fixing.  You kept the reference to dt_probe_desc as a
callback, but the point is that it isn't a callback at all in DTrace v2.  I
expect you want dt_probe_first_match() here.

> -	if ((m = dtrace_probe_iter(dtp, pdp, dt_probe_desc, &pd)) < 0)
> +	if ((m = dt_probe_iter(dtp, pdp, dt_probe_representative, NULL, &prp)) < 0)

Adjust name of callback function.

>  		return NULL; /* dt_errno is set for us */
>  
> -	if ((pvp = dt_provider_lookup(dtp, pd.prv)) == NULL)
> +	if ((pvp = prp->prov) == NULL)
>  		return NULL; /* dt_errno is set for us */
>  
>  	/*
> @@ -1043,10 +1039,6 @@ dt_probe_info(dtrace_hdl_t *dtp, const dtrace_probedesc_t *pdp,
>  		}
>  	}
>  
> -	prp = dt_probe_lookup(dtp, &pd);
> -	if (!prp)
> -		return NULL; /* dt_errno is set for us */
> -
>  	/*
>  	 * Compute the probe description attributes by taking the minimum of
>  	 * the attributes of the specified fields.  If no provider is specified
> -- 
> 2.18.2
> 
> 
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