[PATCH 0/64] Fix CONFIG_DRM_USE_DYNAMIC_DEBUG=y
Jim Cromie
jim.cromie at gmail.com
Wed Jan 8 09:23:39 UTC 2025
This series fixes dynamic-debug's support for DRM, aka
CONFIG_DRM_USE_DYNAMIC_DEBUG=y
Despite a few latent flaws, Classmaps-v1 evaded full review, and got
committed in 2 chunks into lib,include and drm:
b7b4eebdba7b..6ea3bf466ac6 # core dyndbg changes
0406faf25fb1..ee7d633f2dfb # drm adoption
Those flaws:
1. Regression during initialization. classmaps-v1 inits drm-dbg
callsites' static-keys when drm is "modprobed/initd" with
drm.debug=<initval>, but not during driver & helper modprobes.
Previously __drm_debug vs DRM_UT_* was checked at runtime, which made
this a non-issue, but with static-keys set during late initialization,
propagation of classmap to users needed to happen, and didn't.
My test scripts passed dyndbg=<options> to bang on the >control
parser, which obscured this lack of propagation to drivers, and I
didn't pick up on it.
2. DECLARE_DYNDBG_CLASSMAP violated a K&R rule "define once, refer
afterwards", and its designed use in user modules is the root cause
under problem 1.
3. classmaps-v1 was something of a flag-day combo patchset; dyndbg &
DRM parts were overly coupled, and test-dyndbg didn't anticipate and
test for multi-module classes.
Consequently when part 2 went in, we got:
commit bb2ff6c27bc9 ("drm: Disable dynamic debug as broken")
Classmaps-v2 fixes these as follows:
2. replace DECLARE_DYNDBG_CLASSMAP with DYNDBG_CLASSMAP_DEFINE
(invoked once in drm-core) and DYNDBG_CLASSMAP_USE (repeatedly, in
drivers & helpers).
_DEFINE now exports the classmap it creates (in drm.ko), other modules
_USE the classmap, since they want to respond to this class's
settings; by either inputs to /sys/module/drm/parameters/debug or
/prod/dynsmic_debug/control.
_USE adds a usage/linkage record referring to the _DEFINEd (&
exported) classmap, in a new __dyndbg_class_users section (in the
using module). The distinction allows dyndbg to handle the new _USEs
as follows:
1. Now at modprobe, dyndbg scans the new section after the original
__dyndbg_class_maps section, follows the linkage to the _DEFINEr
module, finds the (optional) kernel-param controlling the classmap,
examines its drm.debug=<initval>, and applies it to the module being
initialized.
3. test/validate dyndbg for multi-module classes wo DRM involvement.
A. add test_dynamic_debug_submod.ko, a clone of parent, which _USEs
the parents _DEFINEd classmap. This allows recapitulating various
multi-module scenarios.
B. add tools/testing/selftests/dynamic_debug/*
test now verifies parsing and effect of applied >controls, including
the multi-module scenarios made possible by 3A.
C. to decouple dyndbg from DRM, DECLARE_DYNDBG_CLASSMAP is preserved
until after DRM adapts to the api change. Once DRM drops use, I'll
retire it.
Since the last rev sent here/LKML:
https://lore.kernel.org/lkml/20240716185806.1572048-1-jim.cromie@gmail.com/
Ive rebased onto recent drm-tip, and tested with drm-trybot:
https://patchwork.freedesktop.org/series/139147/
And made the following additions:
1- drop class "protection" special case, per JBaron's preference.
current use is marked BROKEN so nobody to affect.
now framed as policy-choice:
#define ddebug_client_module_protects_classes() false
subsystems wanting protection can change this.
2- compile-time arg-tests in DYNDBG_CLASSMAP_DEFINE
implement several required constraints, and fail obviously.
3- modprobe time check of conflicting class-id reservations
only affects 2+classmaps users.
compile-time solution not apparent.
4- dyndbg can now cause modprobe to fail.
needed to catch 3.
maybe some loose ends here on failure.
5- refactor & rename ddebug_attach_*module_classes
reduce repetetive boilerplate on 2 types: maps, users.
rework mostly brought forward in patchset to reduce churn
TBD: maybe squash more.
Bikeshedding: theres room here to discuss/fix new & old mis-names or
terms, like classmaps vs struct ddebug_class_map, class_user.
Several recent trybot submissions (against drm-tip) have been passing
CI.BAT, and failing one or few CI.IGT tests randomly; re-tests do not
reliably repeat the failures.
its also at github.com:jimc/linux.git
dd-fix-9[st]-ontip & dd-fix-9-13rc
Ive been running it on my desktop w/o issues.
The drivers/gpu/drm patches are RFC, I think there might be a place to
put a single DRM_CLASSMAP_USE(drm_dedbug_classes) to replace the
sprinkling of _USEs in drivers and helpers. IIRC, I tried adding a
_DEFINE into drm_drv.c, that didn't do it, so I punted for now.
I think the dyndbg core additions are ready for review and merging
into a (next-next) test/integration tree.
Jim Cromie (64):
docs/dyndbg: update examples \012 to \n
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
checkpatch: add an exception to the do-while wrapper advice
dyndbg-API: replace DECLARE_DYNDBG_CLASSMAP
dyndbg: check DYNDBG_CLASSMAP_DEFINE args at compile-time
dyndbg: add/use for_subvec() to reduce boilerplate
dyndbg: make proper substructs in _ddebug_info
dyndbg: drop premature optimization in ddebug_add_module
dyndbg: allow ddebug_add_module to fail
dyndbg: rework ddebug_attach_*module_classes()
dyndbg: fail modprobe on ddebug_class_range_overlap()
dyndbg: hoist the range-overlap checks
ddebug: cleanup-range-overlap fails
dyndbg-test: change do_prints testpoint to accept a loopct
selftests-dyndbg: add tools/testing/selftests/dynamic_debug/*
dyndbg-API: promote DYNDBG_CLASSMAP_PARAM to API
dyndbg-doc: add classmap info to howto
dyndbg: treat comma as a token separator
selftests-dyndbg: add comma_terminator_tests
dyndbg: split multi-query strings with %
selftests-dyndbg: test_percent_splitting
docs/dyndbg: explain new delimiters: comma, percent
selftests-dyndbg: add test_mod_submod
docs/dyndbg: explain flags parse 1st
dyndbg: change __dynamic_func_call_cls* macros into expressions
dyndbg: drop "protection" of class'd pr_debugs from legacy queries
drm: use correct ccflags-y spelling
checkpatch: dont warn about unused macro arg on empty body
drm-dyndbg: adapt drm core to use dyndbg classmaps-v2
drm-dyndbg: adapt DRM to invoke DYNDBG_CLASSMAP_PARAM
drm-print: fix config-dependent unused variable
drm-dyndbg: DRM_CLASSMAP_USE in amdgpu driver
drm-dyndbg: DRM_CLASSMAP_USE in i915 driver
drm-dyndbg: DRM_CLASSMAP_USE in drm_crtc_helper
drm-dyndbg: DRM_CLASSMAP_USE in drm_dp_helper
drm-dyndbg: DRM_CLASSMAP_USE in nouveau
drm-dyndbg: add DRM_CLASSMAP_USE to Xe driver
drm-dyndbg: add DRM_CLASSMAP_USE to virtio_gpu
drm-dyndbg: add DRM_CLASSMAP_USE to simpledrm
drm-dyndbg: add DRM_CLASSMAP_USE to bochs
drm-dyndbg: add DRM_CLASSMAP_USE to etnaviv
drm-dyndbg: add DRM_CLASSMAP_USE to gma500 driver
drm-dyndbg: add DRM_CLASSMAP_USE to radeon
drm-dyndbg: add DRM_CLASSMAP_USE to vmwgfx driver
drm-dyndbg: add DRM_CLASSMAP_USE to vkms driver
drm-dyndbg: add DRM_CLASSMAP_USE to udl driver
drm-dyndbg: add DRM_CLASSMAP_USE to mgag200 driver
drm-dyndbg: add DRM_CLASSMAP_USE to the gud driver
drm-dyndbg: add DRM_CLASSMAP_USE to the qxl driver
drm-dyndbg: add DRM_CLASSMAP_USE to the drm_gem_shmem_helper driver
drm: restore CONFIG_DRM_USE_DYNAMIC_DEBUG un-BROKEN
This series fixes dynamic-debug's support for DRM, aka
CONFIG_DRM_USE_DYNAMIC_DEBUG=y
.../admin-guide/dynamic-debug-howto.rst | 115 +++-
MAINTAINERS | 3 +-
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 | 38 +-
drivers/gpu/drm/etnaviv/etnaviv_drv.c | 2 +
drivers/gpu/drm/gma500/psb_drv.c | 2 +
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 | 4 +-
drivers/gpu/drm/tiny/bochs.c | 2 +
drivers/gpu/drm/tiny/simpledrm.c | 2 +
drivers/gpu/drm/udl/udl_main.c | 2 +
drivers/gpu/drm/virtio/virtgpu_drv.c | 2 +
drivers/gpu/drm/vkms/vkms_drv.c | 2 +
drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 2 +
drivers/gpu/drm/xe/xe_drm_client.c | 2 +
include/asm-generic/vmlinux.lds.h | 1 +
include/drm/drm_print.h | 12 +
include/linux/dynamic_debug.h | 193 ++++--
kernel/module/main.c | 15 +-
lib/Kconfig.debug | 24 +-
lib/Makefile | 3 +
lib/dynamic_debug.c | 555 +++++++++++-------
lib/test_dynamic_debug.c | 181 +++---
lib/test_dynamic_debug_submod.c | 17 +
scripts/checkpatch.pl | 3 +-
tools/testing/selftests/Makefile | 1 +
.../testing/selftests/dynamic_debug/Makefile | 9 +
tools/testing/selftests/dynamic_debug/config | 2 +
.../dynamic_debug/dyndbg_selftest.sh | 364 ++++++++++++
38 files changed, 1205 insertions(+), 427 deletions(-)
create mode 100644 lib/test_dynamic_debug_submod.c
create mode 100644 tools/testing/selftests/dynamic_debug/Makefile
create mode 100644 tools/testing/selftests/dynamic_debug/config
create mode 100755 tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
--
2.47.1
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