On Mon, Dec 05, 2022 at 05:34:07PM -0700, Jim Cromie wrote: > Hi everyone, > > DRM_USE_DYNAMIC_DEBUG=y has a regression on rc-* > > Regression is due to a chicken-egg problem loading modules; on > `modprobe i915`, drm is loaded 1st, and drm.debug is set. When > drm_debug_enabled() tested __drm_debug at runtime, that just worked. > > But with DRM_USE_DYNAMIC_DEBUG=y, the runtime test is replaced with a > post-load enablement of drm_dbg/dyndbg callsites (static-keys), via > dyndbg's callback on __drm_debug. Since all drm-drivers need drm.ko, > it is loaded 1st, then drm.debug=X is applied, then drivers load, but > too late for drm_dbgs to be enabled. > > STATUS > > For all-loadable drm,i915,amdgpu configs, it almost works, but > propagating drm.debug to dependent modules doesnt actually apply, > though the motions are there. This is not the problem I want to chase > here. > > The more basic trouble is: > > For builtin drm + helpers, things are broken pretty early; at the > beginning of dynamic_debug_init(). As the ddebug_sanity() commit-msg > describes in some detail, the records added by _USE fail to reference > the struct ddebug_class_map created and exported by _DEFINE, but get > separate addresses to "other" data that segv's when used as the > expected pointer. FWIW, the pointer val starts with "revi". So I honestly have no idea here, linker stuff is way beyond where I have clue. So what's the way forward here? The DEFINE/USE split does like the right thing to do at least from the "how it's used in drivers" pov. But if we're just running circles not quite getting there I dunno :-/ -Daniel > > OVERVIEW > > DECLARE_DYNDBG_CLASSMAP is broken: it is one-size-fits-all-poorly. > It muddles the distinction between a (single) definition, and multiple > references. Something exported should suffice. > > The core of this patchset splits it into: > > DYNDBG_CLASSMAP_DEFINE used once per subsystem to define each classmap > DYNDBG_CLASSMAP_USE declare dependence on a DEFINEd classmap > > This makes the weird coordinated-changes-by-identical-classmaps > "feature" unnecessary; the DEFINE can export the var, and USE refers > to the exported var. > > So this patchset adds another section: __dyndbg_class_refs. > > It is like __dyndbg_classes; it is scanned under ddebug_add_module(), > and attached to each module's ddebug_table. Once attached, it can be > used like classes to validate and apply class FOO >control queries. > > It also maps the class user -> definer explicitly, so that when the > module is loaded, the section scan can find the kernel-param that is > wired to dyndbg's kparam-callback, and apply its state-var, forex: > __drm_debug to the just loaded helper/driver module. > > Theres plenty to address Im sure. > > Jim Cromie (17): > test-dyndbg: fixup CLASSMAP usage error > test-dyndbg: show that DEBUG enables prdbgs at compiletime > dyndbg: fix readback value on LEVEL_NAMES interfaces > dyndbg: replace classmap list with a vector > dyndbg: make ddebug_apply_class_bitmap more selective > dyndbg: dynamic_debug_init - use pointer inequality, not strcmp > dyndbg: drop NUM_TYPE_ARRAY > dyndbg: reduce verbose/debug clutter > dyndbg-API: replace DECLARE_DYNDBG_CLASSMAP with > DYNDBG_CLASSMAP(_DEFINE|_USE) > dyndbg-API: specialize DYNDBG_CLASSMAP_(DEFINE|USE) > dyndbg-API: DYNDBG_CLASSMAP_USE drop extra args > dyndbg-API: DYNDBG_CLASSMAP_DEFINE() improvements > drm_print: fix stale macro-name in comment > dyndbg: unwrap __ddebug_add_module inner function NOTYET > dyndbg: ddebug_sanity() > dyndbg: mess-w-dep-class > dyndbg: miss-on HACK > > drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 14 +- > drivers/gpu/drm/display/drm_dp_helper.c | 14 +- > drivers/gpu/drm/drm_crtc_helper.c | 14 +- > drivers/gpu/drm/drm_print.c | 22 +-- > drivers/gpu/drm/i915/i915_params.c | 14 +- > drivers/gpu/drm/nouveau/nouveau_drm.c | 14 +- > include/asm-generic/vmlinux.lds.h | 3 + > include/drm/drm_print.h | 6 +- > include/linux/dynamic_debug.h | 57 ++++-- > include/linux/map.h | 54 ++++++ > kernel/module/main.c | 2 + > lib/dynamic_debug.c | 240 +++++++++++++++++++----- > lib/test_dynamic_debug.c | 47 ++--- > 13 files changed, 344 insertions(+), 157 deletions(-) > create mode 100644 include/linux/map.h > > -- > 2.38.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
