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Message-ID: <CAJfuBxyYGUpF+n1nHNUS-GtTU9ROi9vx_RQj6kOP1zSMHgM45Q@mail.gmail.com>
Date: Sun, 16 Mar 2025 08:04:38 -0600
From: jim.cromie@...il.com
To: Jim Cromie <jim.cromie@...il.com>, linux-kernel@...r.kernel.org, jbaron@...mai.com,
gregkh@...uxfoundation.org, ukaszb@...omium.org,
intel-gfx-trybot@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
amd-gfx@...ts.freedesktop.org, intel-gvt-dev@...ts.freedesktop.org,
intel-gfx@...ts.freedesktop.org, daniel.vetter@...ll.ch,
tvrtko.ursulin@...ux.intel.com, jani.nikula@...el.com,
ville.syrjala@...ux.intel.com
Subject: Re: [PATCH 05/63] dyndbg: replace classmap list with a vector
On Tue, Feb 25, 2025 at 7:08 AM Louis Chauvet <louis.chauvet@...tlin.com> wrote:
>
>
>
> Le 25/01/2025 ą 07:45, Jim Cromie a écrit :
> > Classmaps are stored in an elf section/array, but are individually
> > list-linked onto dyndbg's per-module ddebug_table for operation.
> >
> > This is unnecessary; even when ddebug_attach_classmap() is handling
> > the builtin section (with classmaps for multiple builtin modules), its
> > contents are ordered, so a module's possibly multiple classmaps will
> > be consecutive in the section, and could be treated as a vector/block,
> > since both start-address and subrange length are in the ddebug_info arg.
> >
> > IOW, this treats classmaps similarly to _ddebugs, which are already
> > kept as vector-refs (address+len).
> >
> > So this changes:
> >
> > struct ddebug_class_map drops list-head link.
> >
> > struct ddebug_table drops the list-head maps, and gets: classes &
> > num_classes for the start-address and num_classes, placed to improve
> > struct packing.
> >
> > The loading: in ddebug_attach_module_classes(), replace the
> > for-the-modname list-add loop, with a forloop that finds the module's
> > subrange (start,length) of matching classmaps within the possibly
> > builtin classmaps vector, and saves those to the ddebug_table.
> >
> > The reading/using: change list-foreach loops in ddebug_class_name() &
> > ddebug_find_valid_class() to walk the array from start to length.
> >
> > Also:
> > Move #define __outvar up, above an added use in a fn-prototype.
> > Simplify ddebug_attach_module_classes args, ref has both address & len.
> >
> > no functional changes
> >
> > Signed-off-by: Jim Cromie <jim.cromie@...il.com>
> > ---
> > include/linux/dynamic_debug.h | 1 -
> > lib/dynamic_debug.c | 61 ++++++++++++++++++-----------------
> > 2 files changed, 32 insertions(+), 30 deletions(-)
> >
> > diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
> > index b9afc7731b7c..2b0057058ecf 100644
> > --- a/include/linux/dynamic_debug.h
> > +++ b/include/linux/dynamic_debug.h
> > @@ -83,7 +83,6 @@ enum class_map_type {
> > };
> >
> > struct ddebug_class_map {
> > - struct list_head link;
> > struct module *mod;
> > const char *mod_name; /* needed for builtins */
> > const char **class_names;
> > diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
> > index 55df35df093b..41cbaa96f83d 100644
> > --- a/lib/dynamic_debug.c
> > +++ b/lib/dynamic_debug.c
> > @@ -45,10 +45,11 @@ extern struct ddebug_class_map __start___dyndbg_classes[];
> > extern struct ddebug_class_map __stop___dyndbg_classes[];
> >
> > struct ddebug_table {
> > - struct list_head link, maps;
> > + struct list_head link;
> > const char *mod_name;
> > - unsigned int num_ddebugs;
> > struct _ddebug *ddebugs;
> > + struct ddebug_class_map *classes;
> > + unsigned int num_ddebugs, num_classes;
> > };
> >
> > struct ddebug_query {
> > @@ -147,13 +148,15 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
> > query->first_lineno, query->last_lineno, query->class_string);
> > }
> >
> > +#define __outvar /* filled by callee */
>
> Hi Jim,
>
> What is the goal of this __outvar define? I can't find any other #define
> of it in the kernel.
its basically a comment, trying to be more important.
if its misleading or overwrought, I can yank it :-)
>
> > static struct ddebug_class_map *ddebug_find_valid_class(struct ddebug_table const *dt,
> > - const char *class_string, int *class_id)
> > + const char *class_string,
> > + __outvar int *class_id)
>
> The order between __outvar and int is not important? Here you have
> __outvar before int, but later [1] the __outvar is after int.
>
I intended no difference, I used it where I thought it communicated best
in each case, and since the macro is empty, it makes none.
> [1]:https://elixir.bootlin.com/linux/v6.14-rc3/source/lib/dynamic_debug.c#L183
>
> Thanks,
> Louis Chauvet
>
> > {
> > struct ddebug_class_map *map;
> > - int idx;
> > + int i, idx;
> >
> > - list_for_each_entry(map, &dt->maps, link) {
> > + for (map = dt->classes, i = 0; i < dt->num_classes; i++, map++) {
> > idx = match_string(map->class_names, map->length, class_string);
> > if (idx >= 0) {
> > *class_id = idx + map->base;
> > @@ -164,7 +167,6 @@ static struct ddebug_class_map *ddebug_find_valid_class(struct ddebug_table cons
> > return NULL;
> > }
> >
> > -#define __outvar /* filled by callee */
> > /*
> > * Search the tables for _ddebug's which match the given `query' and
> > * apply the `flags' and `mask' to them. Returns number of matching
> > @@ -1114,9 +1116,10 @@ static void *ddebug_proc_next(struct seq_file *m, void *p, loff_t *pos)
> >
> > static const char *ddebug_class_name(struct ddebug_iter *iter, struct _ddebug *dp)
> > {
> > - struct ddebug_class_map *map;
> > + struct ddebug_class_map *map = iter->table->classes;
> > + int i, nc = iter->table->num_classes;
> >
> > - list_for_each_entry(map, &iter->table->maps, link)
> > + for (i = 0; i < nc; i++, map++)
> > if (class_in_range(dp->class_id, map))
> > return map->class_names[dp->class_id - map->base];
> >
> > @@ -1200,30 +1203,31 @@ static const struct proc_ops proc_fops = {
> > .proc_write = ddebug_proc_write
> > };
> >
> > -static void ddebug_attach_module_classes(struct ddebug_table *dt,
> > - struct ddebug_class_map *classes,
> > - int num_classes)
> > +static void ddebug_attach_module_classes(struct ddebug_table *dt, struct _ddebug_info *di)
> > {
> > struct ddebug_class_map *cm;
> > - int i, j, ct = 0;
> > + int i, nc = 0;
> >
> > - for (cm = classes, i = 0; i < num_classes; i++, cm++) {
> > + /*
> > + * Find this module's classmaps in a subrange/wholerange of
> > + * the builtin/modular classmap vector/section. Save the start
> > + * and length of the subrange at its edges.
> > + */
> > + for (cm = di->classes, i = 0; i < di->num_classes; i++, cm++) {
> >
> > if (!strcmp(cm->mod_name, dt->mod_name)) {
> > -
> > - v2pr_info("class[%d]: module:%s base:%d len:%d ty:%d\n", i,
> > - cm->mod_name, cm->base, cm->length, cm->map_type);
> > -
> > - for (j = 0; j < cm->length; j++)
> > - v3pr_info(" %d: %d %s\n", j + cm->base, j,
> > - cm->class_names[j]);
> > -
> > - list_add(&cm->link, &dt->maps);
> > - ct++;
> > + if (!nc) {
> > + v2pr_info("start subrange, class[%d]: module:%s base:%d len:%d ty:%d\n",
> > + i, cm->mod_name, cm->base, cm->length, cm->map_type);
> > + dt->classes = cm;
> > + }
> > + nc++;
> > }
> > }
> > - if (ct)
> > - vpr_info("module:%s attached %d classes\n", dt->mod_name, ct);
> > + if (nc) {
> > + dt->num_classes = nc;
> > + vpr_info("module:%s attached %d classes\n", dt->mod_name, nc);
> > + }
> > }
> >
> > /*
> > @@ -1256,10 +1260,9 @@ static int ddebug_add_module(struct _ddebug_info *di, const char *modname)
> > dt->num_ddebugs = di->num_descs;
> >
> > INIT_LIST_HEAD(&dt->link);
> > - INIT_LIST_HEAD(&dt->maps);
> >
> > if (di->classes && di->num_classes)
> > - ddebug_attach_module_classes(dt, di->classes, di->num_classes);
> > + ddebug_attach_module_classes(dt, di);
> >
> > mutex_lock(&ddebug_lock);
> > list_add_tail(&dt->link, &ddebug_tables);
> > @@ -1372,8 +1375,8 @@ static void ddebug_remove_all_tables(void)
> > mutex_lock(&ddebug_lock);
> > while (!list_empty(&ddebug_tables)) {
> > struct ddebug_table *dt = list_entry(ddebug_tables.next,
> > - struct ddebug_table,
> > - link);
> > + struct ddebug_table,
> > + link);
> > ddebug_table_free(dt);
> > }
> > mutex_unlock(&ddebug_lock);
>
> --
> Louis Chauvet, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
>
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