[PATCH v7c 00/24] fix DRM_USE_DYNAMIC_DEBUG=y regression

Jim Cromie
2023-10-18T17:06:15Z

hi Jason, DRM-folk

(v7c now with all checkpatch fixes)

This patchest fixes the chicken-egg initialization problem in the 1st
version of ddebug-class-maps, that DRM-CI uncovered.

The root-problem was DECLARE_DYNDBG_CLASSMAP, which broke the K&R rule:
"define once, refer many". In patch 14 it is replaced by:

DYNDBG_CLASSMAP_DEFINE - define and export a struct ddebug_class_map
DYNDBG_CLASSMAP_USE - ref the exported struct

test-dynamic-debug is also extended with a -submod.ko, in order to
recapitulate the drm & drivers initialization scenario.

They're on v6.6-rc6 now, and recently applied cleanly to drm-tip/drm-tip.

Ive been running recent revs on rc3+, on my desktop and laptop.

The final blocker was a missing __align(8) on the ddebug_class_user
record inserted by DYNDBG_CLASSMAP_USE. This caused DRM=y (builtin
only) to have a corrupt record for drm_kms_helper (a builtin dependent).
Curiously, a clang build did not exhibit this problem.

Heres a part of dmesg, for a DRM=y kernel, booted with
dynamic_debug.verbose=3 drm.debug=0x10

[ 0.466747] dyndbg: add-module: drm 406 sites
[ 0.467569] dyndbg: classes[0]: module:drm base:0 len:10 type:DISJOINT_BITS
[ 0.467743] dyndbg: module:drm attached 1 classes
[ 0.468557] dyndbg: builtin class: module:drm base:0 len:10 type:DISJOINT_BITS
[ 0.468742] dyndbg: found kp:drm.debug =0x10
[ 0.468743] dyndbg: mapped to: module:drm base:0 len:10 type:DISJOINT_BITS
[ 0.469742] dyndbg: drm.debug: classbits: 0x10
[ 0.470573] dyndbg: apply bitmap: 0x10 to: 0x0 for drm
[ 0.470743] dyndbg: query 0: "class DRM_UT_ATOMIC +p" mod:drm
[ 0.471743] dyndbg: split into words: "class" "DRM_UT_ATOMIC" "+p"
[ 0.472743] dyndbg: op='+' flags=0x1 maskp=0xffffffff
[ 0.473679] dyndbg: parsed: func="" file="" module="drm" format="" lineno=0-0 class=DRM_UT_ATOMIC
[ 0.473749] dyndbg: processed 1 queries, with 0 matches, 0 errs
[ 0.474742] dyndbg: bit_4: 0 matches on class: DRM_UT_ATOMIC -> 0x10
[ 0.475742] dyndbg: applied bitmap: 0x10 to: 0x0 for drm
[ 0.476686] dyndbg: 406 debug prints in module drm
[ 0.476743] dyndbg: add-module: drm_kms_helper 93 sites
[ 0.477727] dyndbg: class_ref[0] drm_kms_helper -> drm module:drm base:0 len:10 type:DISJOINT_BITS
[ 0.477743] dyndbg: builtin class: module:drm base:0 len:10 type:DISJOINT_BITS
[ 0.478742] dyndbg: found kp:drm.debug =0x10
[ 0.478743] dyndbg: mapped to: module:drm base:0 len:10 type:DISJOINT_BITS
[ 0.479743] dyndbg: drm.debug: classbits: 0x10
[ 0.480592] dyndbg: apply bitmap: 0x10 to: 0x0 for drm_kms_helper
[ 0.480743] dyndbg: query 0: "class DRM_UT_ATOMIC +p" mod:drm_kms_helper
[ 0.481743] dyndbg: split into words: "class" "DRM_UT_ATOMIC" "+p"
[ 0.482743] dyndbg: op='+' flags=0x1 maskp=0xffffffff
[ 0.483743] dyndbg: parsed: func="" file="" module="drm_kms_helper" format="" lineno=0-0 class=DRM_UT_ATOMIC
[ 0.484750] dyndbg: class-ref: drm_kms_helper.DRM_UT_ATOMIC module:drm_kms_helper nd:93 nc:0 nu:1
[ 0.485809] dyndbg: processed 1 queries, with 44 matches, 0 errs
[ 0.486742] dyndbg: bit_4: 44 matches on class: DRM_UT_ATOMIC -> 0x10
[ 0.487742] dyndbg: applied bitmap: 0x10 to: 0x0 for drm_kms_helper
[ 0.488743] dyndbg: attach-client-module: module:drm_kms_helper nd:93 nc:0 nu:1
[ 0.489742] dyndbg: 93 debug prints in module drm_kms_helper

Widespread testing is appreciated.
I have scripts if anyone wants them.
lkp-robot reported success on dd-fix-7b, no report yet on 7c

Patches are also at https://github.com/jimc/linux/tree/dd-fix-7c

Jim Cromie (24):
test-dyndbg: fixup CLASSMAP usage error
dyndbg: reword "class unknown," to "class:_UNKNOWN_"
dyndbg: make ddebug_class_param union members same size
dyndbg: replace classmap list with a vector
dyndbg: ddebug_apply_class_bitmap - add module arg, select on it
dyndbg: split param_set_dyndbg_classes to module/wrapper fns
dyndbg: drop NUM_TYPE_ARRAY
dyndbg: reduce verbose/debug clutter
dyndbg: silence debugs with no-change updates
dyndbg: tighten ddebug_class_name() 1st arg type
dyndbg: tighten fn-sig of ddebug_apply_class_bitmap
dyndbg: reduce verbose=3 messages in ddebug_add_module
dyndbg-API: remove DD_CLASS_TYPE_(DISJOINT|LEVEL)_NAMES and code
dyndbg-API: fix CONFIG_DRM_USE_DYNAMIC_DEBUG regression
dyndbg: refactor ddebug_classparam_clamp_input
dyndbg-API: promote DYNDBG_CLASSMAP_PARAM to API
dyndbg-doc: add classmap info to howto
dyndbg: reserve flag bit _DPRINTK_FLAGS_PREFIX_CACHED
dyndbg: add _DPRINTK_FLAGS_INCL_LOOKUP
dyndbg: refactor *dynamic_emit_prefix
dyndbg: change WARN_ON to WARN_ON_ONCE
drm: use correct ccflags-y spelling
drm-drivers: DRM_CLASSMAP_USE in 2nd batch of drivers, helpers
drm: restore CONFIG_DRM_USE_DYNAMIC_DEBUG un-BROKEN

.../admin-guide/dynamic-debug-howto.rst | 60 ++-
MAINTAINERS | 2 +-
drivers/gpu/drm/Kconfig | 3 +-
drivers/gpu/drm/Makefile | 3 +-
drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 12 +-
drivers/gpu/drm/display/drm_dp_helper.c | 12 +-
drivers/gpu/drm/drm_crtc_helper.c | 12 +-
drivers/gpu/drm/drm_gem_shmem_helper.c | 2 +
drivers/gpu/drm/drm_print.c | 35 +-
drivers/gpu/drm/gud/gud_drv.c | 2 +
drivers/gpu/drm/i915/i915_params.c | 12 +-
drivers/gpu/drm/mgag200/mgag200_drv.c | 2 +
drivers/gpu/drm/nouveau/nouveau_drm.c | 12 +-
drivers/gpu/drm/qxl/qxl_drv.c | 2 +
drivers/gpu/drm/radeon/radeon_drv.c | 2 +
drivers/gpu/drm/udl/udl_main.c | 2 +
drivers/gpu/drm/vkms/vkms_drv.c | 2 +
drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 2 +
include/asm-generic/vmlinux.lds.h | 1 +
include/drm/drm_print.h | 12 +-
include/linux/dynamic_debug.h | 121 +++--
kernel/module/main.c | 3 +
lib/Kconfig.debug | 24 +-
lib/Makefile | 3 +
lib/dynamic_debug.c | 458 +++++++++++-------
lib/test_dynamic_debug.c | 131 ++---
lib/test_dynamic_debug_submod.c | 17 +
27 files changed, 584 insertions(+), 365 deletions(-)
create mode 100644 lib/test_dynamic_debug_submod.c

--
2.41.0