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Date: Fri, 13 Aug 2021 18:51:05 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Jim Cromie <jim.cromie@...il.com>
Cc: gregkh@...uxfoundation.org, seanpaul@...omium.org,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
Alex Deucher <alexander.deucher@....com>,
Christian König <christian.koenig@....com>,
"Pan, Xinhui" <Xinhui.Pan@....com>,
Harry Wentland <harry.wentland@....com>,
Leo Li <sunpeng.li@....com>,
Zhenyu Wang <zhenyuw@...ux.intel.com>,
Zhi Wang <zhi.a.wang@...el.com>,
Jani Nikula <jani.nikula@...ux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Jason Baron <jbaron@...mai.com>,
Hawking Zhang <Hawking.Zhang@....com>,
Tao Zhou <tao.zhou1@....com>, Huang Rui <ray.huang@....com>,
Kevin Wang <kevin1.wang@....com>,
Chengming Gui <Jack.Gui@....com>,
Likun Gao <Likun.Gao@....com>,
John Clements <john.clements@....com>,
Ashley Thomas <Ashley.Thomas2@....com>,
Qingqing Zhuo <qingqing.zhuo@....com>,
Aurabindo Pillai <aurabindo.pillai@....com>,
Wyatt Wood <Wyatt.Wood@....com>,
Johan Hovold <johan@...nel.org>, Jessica Yu <jeyu@...nel.org>,
Joe Perches <joe@...ches.com>, Miguel Ojeda <ojeda@...nel.org>,
Nick Desaulniers <ndesaulniers@...ogle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Masahiro Yamada <masahiroy@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
"Paul E. McKenney" <paulmck@...nel.org>,
Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
Thomas Gleixner <tglx@...utronix.de>,
Vitor Massaru Iha <vitor@...saru.org>,
Sedat Dilek <sedat.dilek@...il.com>,
Changbin Du <changbin.du@...el.com>,
Marco Elver <elver@...gle.com>,
Jarkko Sakkinen <jarkko@...nel.org>,
Alexander Potapenko <glider@...gle.com>,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Zhen Lei <thunder.leizhen@...wei.com>,
Albert van der Linde <alinde@...gle.com>,
Johannes Berg <johannes.berg@...el.com>,
Arvind Sankar <nivedita@...m.mit.edu>,
Patricia Alfonso <trishalfonso@...gle.com>,
Arnd Bergmann <arnd@...db.de>,
Palmer Dabbelt <palmerdabbelt@...gle.com>,
Jiri Olsa <jolsa@...nel.org>,
Andrey Konovalov <andreyknvl@...il.com>,
linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
amd-gfx@...ts.freedesktop.org, intel-gvt-dev@...ts.freedesktop.org,
intel-gfx@...ts.freedesktop.org
Subject: Re: [PATCH v5 3/9] dyndbg: add DEFINE_DYNAMIC_DEBUG_CATEGORIES and
callbacks
On Fri, Aug 13, 2021 at 09:17:11AM -0600, Jim Cromie wrote:
> DEFINE_DYNAMIC_DEBUG_CATEGORIES(name, var, bitmap_desc, @bit_descs)
> allows users to define a drm.debug style (bitmap) sysfs interface, and
> to specify the desired mapping from bits[0-N] to the format-prefix'd
> pr_debug()s to be controlled.
>
> DEFINE_DYNAMIC_DEBUG_CATEGORIES(debug_gvt, __gvt_debug,
> "i915/gvt bitmap desc",
> /**
> * search-prefixes, passed to dd-exec_queries
> * defines bits 0-N in order.
> * leading ^ is tacitly inserted (by callback currently)
> * trailing space used here excludes subcats.
> * helper macro needs more work
> * macro to autogen ++$i, 0x%x$i ?
> */
> _DD_cat_("gvt:cmd: "),
> _DD_cat_("gvt:core: "),
> _DD_cat_("gvt:dpy: "),
> _DD_cat_("gvt:el: "),
> _DD_cat_("gvt:irq: "),
> _DD_cat_("gvt:mm: "),
> _DD_cat_("gvt:mmio: "),
> _DD_cat_("gvt:render: "),
> _DD_cat_("gvt:sched: "));
>
> dynamic_debug.c: add 3 new elements:
>
> - int param_set_dyndbg()
> - int param_get_dyndbg()
> - struct kernel_param_ops param_ops_dyndbg
>
> Following the model of kernel/params.c STANDARD_PARAM_DEFS, All 3 are
> non-static and exported.
>
> dynamic_debug.h:
>
> Add DEFINE_DYNAMIC_DEBUG_CATEGORIES() described above, and a do-nothing stub.
>
> Note that it also calls MODULE_PARM_DESC for the user, but expects the
> user to catenate all the bit-descriptions together (as is done in
> drm.debug), and in the following uses in amdgpu, i915.
>
> This in the hope that someone can offer an auto-incrementing
> label-generating macro, producing "\tbit-4 0x10\t" etc, and can show
> how to apply it to __VA_ARGS__.
>
> Also extern the struct kernel_param param_ops_dyndbg symbol, as is
> done in moduleparams.h for all the STANDARD params.
>
> USAGE NOTES:
>
> Using dyndbg to query on "format ^$prefix" requires that the prefix be
> present in the compiled-in format string; where run-time prefixing is
> used, that format would be "%s...", which is not usefully selectable.
>
> Adding structural query terms (func,file,lineno) could help (module is
> already done), but DEFINE_DYNAMIC_DEBUG_CATEGORIES can't do that now,
> adding it needs a better reason imo.
>
> Dyndbg is completely agnostic wrt the categorization scheme used, to
> play well with any prefix convention already in use. Ad-hoc
> categories and sub-categories are implicitly allowed, author
> discipline and review is expected.
>
> Here are some examples:
>
> "1","2","3" 2 doesnt imply 1.
> otherwize, sorta like printk levels
> "1:","2:","3:" are better, avoiding [1-9]\d+ ambiguity
> "hi:","mid:","low:" are reasonable, and imply independence
> "todo:","rfc:" might be handy
> "A:".."Z:" uhm, yeah
>
> Hierarchical classes/categories are natural:
>
> "drm:<CAT>:" is used in later commit
> "drm:<CAT>:<SUB>:" is a natural extension.
> "drm:atomic:fail:" has been proposed, sounds directly useful
>
> Some properties of a hierarchical category deserve explication:
>
> Trailing spaces matter !
>
> With 1..3-space ("drm: ", "drm:atomic: ", "drm:atomic:fail: "), the
> ":" doesnt terminate the search-space, the trailing space does.
> So a "drm:" search specification will match all DRM categories &
> subcategories, and will not be useful in an interface where all
> categories are controlled together. That said, "drm:atomic:" &
> "drm:atomic: " are different, and both are useful in cases.
>
> Ad-Hoc sub-categories:
>
> These have a caveat wrt wrapper macros adding prefixes like
> "drm:atomic: "; the trailing space in the prefix means that
> drm_dbg("fail: ...") renders as "drm:atomic: fail: ", which obviously
> isn't ideal wrt clear and simple bitmaps.
>
> A possible solution is to have a FOO_() version of every FOO() macro
> which (anti-mnemonically) elides the trailing space, which is normally
> inserted by a modified FOO(). Doing this would enforce a policy
> decision that "debug categories will be space terminated", with an
> pressure-relief valve.
>
> Summarizing:
>
> - "drm:kms: " & "drm:kms:" are different
> - "drm:kms" also different - includes drm:kms2:
> - "drm:kms:\t" also different
> - "drm:kms:*" doesnt work, no wildcard on format atm.
>
> Order matters in DEFINE_DYNAMIC_DEBUG_CATEGORIES(... @bit_descs)
>
> @bit_descs (array) position determines the bit mapping to the prefix,
> so to keep a stable map, new categories or 3rd level categories must
> be added to the end.
>
> Since bits are/will-stay applied 0-N, the later bits can countermand
> the earlier ones, but its tricky - consider;
>
> DD_CATs(... "drm:atomic:", ""drm:atomic:fail:" ) // misleading
>
> The 1st search-term is misleading, because it includes (modifies)
> subcategories, but then 2nd overrides it. So don't do that.
>
> There is still plenty of bikeshedding to do.
> ---
> v4+:
>
> . rename to DEFINE_DYNAMIC_DEBUG_CATEGORIES from DEFINE_DYNDBG_BITMAP
> . in query, replace hardcoded "i915" w kp->mod->name
> . static inline the stubs
> . const *str in structs, const array. -Emil
> . dyndbg: add do-nothing DEFINE_DYNAMIC_DEBUG_CATEGORIES if !DD_CORE
> . call MOD_PARM_DESC(name, "$desc") for users
> . simplify callback, remove bit-change detection
> . config errs reported by <lkp@...el.com>
>
> ddh-helpers
> Signed-off-by: Jim Cromie <jim.cromie@...il.com>
So, it is signed or not? I didn't get (perhaps due to misplaced changlog?).
...
> } __attribute__((aligned(8)));
>
>
Do we need two blank lines here?
> +struct kernel_param;
...
> +int param_set_dyndbg(const char *instr, const struct kernel_param *kp)
> +{
> + unsigned long inbits;
> + int rc, i, chgct = 0, totct = 0;
> + char query[OUR_QUERY_SIZE];
> + struct dyndbg_bitdesc *bitmap = (struct dyndbg_bitdesc *) kp->data;
So you need space after ')' ?
> + rc = kstrtoul(instr, 0, &inbits);
> + if (rc) {
> + pr_err("set_dyndbg: failed\n");
> + return -EINVAL;
Why not to return rc?
> + }
> + vpr_info("set_dyndbg: input 0x%lx\n", inbits);
> +
> + for (i = 0; !!bitmap[i].prefix; i++) {
Hmm... Why not simply
for (bitmap = ...; bitmap->prefix; bitmap++) {
?
> +
Redundant blank line.
> + sprintf(query, "format '^%s' %cp", bitmap[i].prefix,
> + test_bit(i, &inbits) ? '+' : '-');
snprintf() ?
> +
> + chgct = dynamic_debug_exec_queries(query, kp->mod->name);
> +
> + v2pr_info("bit-%d: %d changes by '%s'\n", i, chgct, query);
> + totct += chgct;
> + }
> + vpr_info("total changes: %d\n", totct);
> + return 0;
> +}
...
> + return scnprintf(buffer, PAGE_SIZE, "%u\n",
> + *((unsigned int *)kp->arg));
One line.
--
With Best Regards,
Andy Shevchenko
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