Re: [DTrace-devel] [PATCH 05/14] Add a hook for a provider-specific "update" function

[Kris Van Hees <kris.van.hees@oracle.com>]

Much like the previous patch not considering the generic nature of retained
enablings, this one should be part of that design also.  The functionality
we need to handle match-after-start probe specifications really should be
independent from any specific provider.  It may (well, almost certainly will)
require a hook in providers that need to do special handling.  But that would
be a specific hook for a specific purpose - not just an 'update' hook.

On Tue, Jun 04, 2024 at 02:11:04PM -0400, eugene.loh--- via DTrace-devel wrote:
> From: Eugene Loh <eugene.loh@oracle.com>
> 
> For up-coming USDT-probe support, we need to update a BPF map
> -- at least when the dtrace session starts but possibly also later
> to support systemwide USDT tracing for processes that may start up
> later.
> 
> One way to do this is with a USDT-specific update function.
> 
> For now, let's add a hook for providers to have provider-specific
> update functions.  User space can either call
> 
>     for (i = 0; i < ARRAY_SIZE(dt_providers); i++) {
>         if (dt_providers[i]->update)
>             dt_providers[i]->update(...);
>     }
> 
> any time it likes.  Or it can call dt_usdt.update(...).
> 
> This is for WIP.  A different approach can be adopted later instead.
> 
> Signed-off-by: Eugene Loh <eugene.loh@oracle.com>
> ---
>  libdtrace/dt_provider.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/libdtrace/dt_provider.h b/libdtrace/dt_provider.h
> index 17b1844c..21ff15ad 100644
> --- a/libdtrace/dt_provider.h
> +++ b/libdtrace/dt_provider.h
> @@ -68,6 +68,8 @@ typedef struct dt_provimpl {
>  			      void *datap);
>  	void (*destroy)(dtrace_hdl_t *dtp,	/* free provider data */
>  			      void *datap);
> +	void (*update)(dtrace_hdl_t *dtp,	/* update provider-specific info */
> +			      void *datap);
>  } dt_provimpl_t;
>  
>  /* list dt_dtrace first */
> -- 
> 2.18.4
> 
> 
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