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:" ) // misleadingThe 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@intel.com
ddh-helpers
Signed-off-by: Jim Cromie jim.cromie@gmail.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.