Re: [PATCH v2 09/15] dyndbg: add trace destination field to _ddebug

[jim . cromie]

On Thu, Nov 30, 2023 at 4:41 PM Łukasz Bartosik <lb@xxxxxxxxxxxx> wrote:
>
> Add trace destination field (trace_dst) to the _ddebug structure.
> The trace destination field is used to determine output of debug
> logs when +T is set. Setting trace_dst value to TRACE_DST_BITS(63)
> enables output to prdbg and devdbg trace events. Setting trace_dst
> value to a value in range of [0..62] enables output to trace instance.
>

FWIW, I think setting trace_dest = 0  maps naturally to global / event buf.
The reason class_id DFLT is 63 is that DRM_UT_CORE is 0,
and DFLT allowed it to remain unchanged.


> Signed-off-by: Łukasz Bartosik <lb@xxxxxxxxxxxx>
> ---
>  include/linux/dynamic_debug.h | 14 ++++++++++++--
>  lib/dynamic_debug.c           | 28 +++++++++++++++++++---------
>  2 files changed, 31 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
> index 684766289bfc..56f152e75604 100644
> --- a/include/linux/dynamic_debug.h
> +++ b/include/linux/dynamic_debug.h
> @@ -60,9 +60,19 @@ struct _ddebug {
>  #else
>  #define _DPRINTK_FLAGS_DEFAULT 0
>  #endif
> -       struct {
> +       struct dd_ctrl {
>                 unsigned int flags:8;
> -               unsigned unused:24;
> +       /*
> +        * The trace destination field is used to determine output of debug
> +        * logs when +T is set. Setting trace_dst value to TRACE_DST_MAX(63)
> +        * enables output to prdbg and devdbg trace events. Setting trace_dst
> +        * value to a value in range of [0..62] enables output to trace
> +        * instance.
> +        */
> +#define TRACE_DST_BITS 6
> +               unsigned int trace_dst:TRACE_DST_BITS;
> +#define TRACE_DST_MAX  ((1 << TRACE_DST_BITS) - 1)
> +               unsigned unused:18;
>         } ctrl;
>  } __attribute__((aligned(8)));
>
> diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
> index f47cb76e0e3d..0dc9ec76b867 100644
> --- a/lib/dynamic_debug.c
> +++ b/lib/dynamic_debug.c
> @@ -80,14 +80,24 @@ module_param(verbose, int, 0644);
>  MODULE_PARM_DESC(verbose, " dynamic_debug/control processing "
>                  "( 0 = off (default), 1 = module add/rm, 2 = >control summary, 3 = parsing, 4 = per-site changes)");
>
> +static inline struct dd_ctrl *get_ctrl(struct _ddebug *desc)
> +{
> +       return &desc->ctrl;
> +}
> +
> +static inline void set_ctrl(struct _ddebug *desc, struct dd_ctrl *ctrl)
> +{
> +       desc->ctrl = *ctrl;
> +}
> +
>  static inline unsigned int get_flags(const struct _ddebug *desc)
>  {
>         return desc->ctrl.flags;
>  }
>
> -static inline void set_flags(struct _ddebug *desc, unsigned int val)
> +static inline unsigned int get_trace_dst(const struct _ddebug *desc)
>  {
> -       desc->ctrl.flags = val;
> +       return desc->ctrl.trace_dst;
>  }
>
>  /* Return the path relative to source root */
> @@ -190,8 +200,8 @@ static int ddebug_change(const struct ddebug_query *query,
>  {
>         int i;
>         struct ddebug_table *dt;
> -       unsigned int newflags;
>         unsigned int nfound = 0;
> +       struct dd_ctrl nctrl = {0};
>         struct flagsbuf fbuf, nbuf;
>         struct ddebug_class_map *map = NULL;
>         int __outvar valid_class;
> @@ -257,14 +267,14 @@ static int ddebug_change(const struct ddebug_query *query,
>
>                         nfound++;
>
> -                       newflags = (get_flags(dp) & modifiers->mask) | modifiers->flags;
> -                       if (newflags == get_flags(dp))
> +                       nctrl.flags = (get_flags(dp) & modifiers->mask) | modifiers->flags;
> +                       if (!memcmp(&nctrl, get_ctrl(dp), sizeof(struct dd_ctrl)))
>                                 continue;
>  #ifdef CONFIG_JUMP_LABEL
>                         if (get_flags(dp) & _DPRINTK_FLAGS_ENABLED) {
> -                               if (!(newflags & _DPRINTK_FLAGS_ENABLED))
> +                               if (!(nctrl.flags & _DPRINTK_FLAGS_ENABLED))
>                                         static_branch_disable(&dp->key.dd_key_true);
> -                       } else if (newflags & _DPRINTK_FLAGS_ENABLED) {
> +                       } else if (nctrl.flags & _DPRINTK_FLAGS_ENABLED) {
>                                 static_branch_enable(&dp->key.dd_key_true);
>                         }
>  #endif
> @@ -272,8 +282,8 @@ static int ddebug_change(const struct ddebug_query *query,
>                                   trim_prefix(dp->filename), dp->lineno,
>                                   dt->mod_name, dp->function,
>                                   ddebug_describe_flags(get_flags(dp), &fbuf),
> -                                 ddebug_describe_flags(newflags, &nbuf));
> -                       set_flags(dp, newflags);
> +                                 ddebug_describe_flags(nctrl.flags, &nbuf));
> +                       set_ctrl(dp, &nctrl);
>                 }
>         }
>         mutex_unlock(&ddebug_lock);
> --
> 2.43.0.rc2.451.g8631bc7472-goog
>