| Message ID | 20221206003424.592078-1-jim.cromie@gmail.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | DRM_USE_DYNAMIC_DEBUG regression | expand |
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 >
On Wed, Jan 11, 2023 at 4:09 PM Daniel Vetter <daniel@ffwll.ch> wrote: > > 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? > Ive fixed this aspect. Unsurprisingly, it wasnt the linker :-} > 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 > Sending new rev next. I think its getting close.
On Fri, Jan 13, 2023 at 11:29:57AM -0700, jim.cromie@gmail.com wrote: > On Wed, Jan 11, 2023 at 4:09 PM Daniel Vetter <daniel@ffwll.ch> wrote: > > > > 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? > > > > Ive fixed this aspect. > Unsurprisingly, it wasnt the linker :-} Awesome! > > 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 > > > > Sending new rev next. > I think its getting close. Thanks a lot for keeping on pushing this. -Daniel
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". 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