Re: [PATCH v8-RESEND 00/33] Fix CONFIG_DRM_USE_DYNAMIC_DEBUG=y regression

From: Łukasz Bartosik
Date: Tue May 21 2024 - 07:41:19 EST

On Thu, May 16, 2024 at 7:44 PM Jim Cromie <jim.cromie@xxxxxxxxx> wrote:
>
> hi Greg, Jason,
>
> This patchset fixes the CONFIG_DRM_USE_DYNAMIC_DEBUG=y regression,
> Fixes: bb2ff6c27bc9 ("drm: Disable dynamic debug as broken")
>
> Im calling it v8, to keep consistent with previous labels.
> v6 was what got committed, back in 9/2022.
> v7 had at least 2 problems that blocked its submission:
>
> https://lore.kernel.org/lkml/20231101002609.3533731-1-jim.cromie@xxxxxxxxx/
> https://patchwork.freedesktop.org/series/125066/
>
> 1. missing __align(8) in METATDATA macro, giving too much placement
> freedom to linker, caused weird segvs following non-ptr vals, but for
> builtin modules only. found by lkp-test.
>
> 2. the main patch touched 2 subsystems at once, which would require
> special handling.
>
> What was broken about DYNAMIC_DEBUG ?
>
> Booting a modular kernel with drm.debug=0x1ff enabled pr_debugs only
> in drm itself, not in the yet-to-be loaded driver + helpers. Once
> loaded, the driver's pr_debugs are properly enabled by:
>
> echo 0x1ff > /sys/module/drm/parameters/debug # still worked
>
> I had tested with scripts doing lots of modprobes with various
> permutations of dyndbg=<> option, and I missed that I didn't test
> without them.
>
> The deeper cause was my design error, a violation of the K&R rule:
> "define once, refer many times".
>
> DECLARE_DYNDBG_CLASSMAP defined the classmap, and was used everywhere,
> re-declaring the same static classmap repeatedly. Jani Nikula actually
> picked up on this (iirc shortly after committed), but the problem
> hadn't been seen yet in CI. One patchset across 2 subsystems didn't
> help either.
>

Could you summarize classmaps from the beginning ?


> So the revised classmap API "splits" it to def & ref:
>
> DYNDBG_CLASSMAP_DEFINE fixes & updates the busted macro, EXPORTing the
> classmap instead. It gets invoked once per subsystem, by the
> parent/builtin, drm.ko for DRM.
>
> DYNDBG_CLASSMAP_USE in drivers and helpers refer to the classmap by
> name, which links the 2 modules, (like a driver's dependency on extern
> __drm_debug).
>
> These 2 tell dyndbg to map "class FOO" to the defined FOO_ID, which
> allows it to make those changes via >control, in both class definer
> modules and dependent modules.
>
> DYNDBG_CLASSMAP_PARAM*, defines the controlling kparam, and binds it
> to both the _var, and the _DEFINEd classmap. So drm uses this to bind
> the classmap to __drm_debug.
>
> It provides the common control-point for the sub-system; it is applied
> to the class'd pr_debugs during modprobe of both _DEFINEr and USErs.
> It also enforces the relative nature of LEVEL classmaps, ie V3>V2.
>
> DECLARE_DYNDBG_CLASSMAP is preserved to decouple the DRM patches, so
> they can be applied later. I've included them for anyone who wants to
> test against DRM now.
>
> A new struct and elf section contain the _USEs; on modprobe, these are
> scanned similarly to the _DEFINEs, but follow the references to their
> defining modules, find the kparam wired to the classmap, and apply its
> classmap settings to the USEr. This action is what V1 missed, which
> is why drivers failed to enable debug during modprobe.
>
> In order to recapitulate the regression scenario without involving
> DRM, the patchset adds test_dynamic_debug_submod, which is a duplicate
> of its parent; _submod.c #defines _SUBMOD, and then includes parent.
>
> This puts _DEFINE and _USE close together in the same file, for
> obviousness, and to guarantee that the submod always has the same
> complement of debug()s, giving consistent output from both when
> classmaps are working properly.
>
> Also ./tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh adds a
> turn-key selftest. I pulled it forward from a dyndbg-to-trace patchset
> that I and Lukasz Bartozik have been working out.
>
> It works nicely from virtme-ng:
>
> [jimc@frodo vx]$ vrun_ -- ./tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
> doing: vng --verbose --name v6.9-rc5-34-g2f1ace6e1c68 \
> --user root --cwd ../.. \
> -a dynamic_debug.verbose=2 -p 4 \
> -- ./tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
> virtme: waiting for virtiofsd to start
> ...
> [ 3.546739] ip (260) used greatest stack depth: 12368 bytes left
> [ 3.609288] virtme-init: starting script
> test_dynamic_debug_submod not there
> test_dynamic_debug not there
> # BASIC_TESTS
> ...
> # Done on: Fri Apr 26 20:45:08 MDT 2024
> [ 4.765751] virtme-init: script returned {0}
> Powering off.
> [ 4.805790] ACPI: PM: Preparing to enter system sleep state S5
> [ 4.806223] kvm: exiting hardware virtualization
> [ 4.806564] reboot: Power down
> [jimc@frodo vx]$
>
>
> I've been running the kernel on my x86 desktop & laptop, booting with
> drm.debug=0x1f, then turning it all-off after sleep 15.
>
> a few highlights from a bare-metal boot:
>
> here modprobe amdgpu; dyndbg applies last bit/class/category, and
> finishes init, then drm and amdgpu start logging as they execute
>
> [ 9.019696] gandalf kernel: dyndbg: query 0: "class DRM_UT_ATOMIC +p" mod:amdgpu
> [ 9.019704] gandalf kernel: dyndbg: class-ref: amdgpu.DRM_UT_ATOMIC module:amdgpu nd:4754 nc:0 nu:1
> [ 9.020012] gandalf kernel: dyndbg: processed 1 queries, with 21 matches, 0 errs
> [ 9.020017] gandalf kernel: dyndbg: bit_4: 21 matches on class: DRM_UT_ATOMIC -> 0x1f
> [ 9.020021] gandalf kernel: dyndbg: applied bitmap: 0x1f to: 0x0 for amdgpu
> [ 9.020026] gandalf kernel: dyndbg: attach-client-module: module:amdgpu nd:4754 nc:0 nu:1
> [ 9.020031] gandalf kernel: dyndbg: 4754 debug prints in module amdgpu
> [ 9.055065] gandalf kernel: [drm] amdgpu kernel modesetting enabled.
> [ 9.055138] gandalf kernel: [drm:amdgpu_acpi_detect [amdgpu]] No matching acpi device found for AMD3000
> [ 9.055564] gandalf kernel: amdgpu: Virtual CRAT table created for CPU
> [ 9.055585] gandalf kernel: amdgpu: Topology: Add CPU node
> [ 9.055752] gandalf kernel: amdgpu 0000:0c:00.0: enabling device (0006 -> 0007)
> [ 9.055821] gandalf kernel: [drm] initializing kernel modesetting (NAVI10 0x1002:0x731F 0x148C:0x2398 0xC1).
> [ 9.055835] gandalf kernel: [drm] register mmio base: 0xFCB00000
> [ 9.055839] gandalf kernel: [drm] register mmio size: 524288
> [ 9.059148] gandalf kernel: [drm:amdgpu_discovery_set_ip_blocks [amdgpu]] number of dies: 1
> [ 9.059387] gandalf kernel: [drm:amdgpu_discovery_set_ip_blocks [amdgpu]] number of hardware IPs on die0: 39
> [ 9.059623] gandalf kernel: [drm:amdgpu_discovery_set_ip_blocks [amdgpu]] ATHUB(35) #0 v2.0.0:
> [ 9.059856] gandalf kernel: [drm:amdgpu_discovery_set_ip_blocks [amdgpu]] 0x00000c00
> [ 9.060096] gandalf kernel: [drm:amdgpu_discovery_set_ip_blocks [amdgpu]] 0x02408c00
> [ 9.060328] gandalf kernel: [drm:amdgpu_discovery_set_ip_blocks [amdgpu]] set register base offset for ATHUB
>
> a startup script, after sleep 15, turns off the logging:
>
> echo 0 > /sys/module/drm/parameters/debug
>
> heres 1st 2 bits/classes/categories being turned off:
>
> [ 29.105991] gandalf kernel: [drm:amdgpu_ih_process [amdgpu]] amdgpu_ih_process: rptr 90752, wptr 90784
> [ 29.118086] gandalf kernel: dyndbg: bits:0x0 > *.debug
> [ 29.118096] gandalf kernel: dyndbg: apply bitmap: 0x0 to: 0x1f for '*'
> [ 29.118102] gandalf kernel: dyndbg: query 0: "class DRM_UT_CORE -p" mod:*
> [ 29.118122] gandalf kernel: dyndbg: good-class: drm.DRM_UT_CORE module:drm nd:338 nc:1 nu:0
> [ 29.119548] gandalf kernel: dyndbg: class-ref: drm_kms_helper.DRM_UT_CORE module:drm_kms_helper nd:93
> nc:0 nu:1
> [ 29.119552] gandalf kernel: dyndbg: class-ref: drm_display_helper.DRM_UT_CORE module:drm_display_helper nd:151 nc:0 nu:1
> [ 29.119737] gandalf kernel: dyndbg: class-ref: amdgpu.DRM_UT_CORE module:amdgpu nd:4754 nc:0 nu:1
> [ 29.122181] gandalf kernel: [drm:amdgpu_ih_process [amdgpu]] amdgpu_ih_process: rptr 90784, wptr 90816
> [ 29.127687] gandalf kernel: dyndbg: processed 1 queries, with 466 matches, 0 errs
> [ 29.127690] gandalf kernel: dyndbg: bit_0: 466 matches on class: DRM_UT_CORE -> 0x0
> [ 29.127692] gandalf kernel: dyndbg: query 0: "class DRM_UT_DRIVER -p" mod:*
> [ 29.127696] gandalf kernel: dyndbg: good-class: drm.DRM_UT_DRIVER module:drm nd:338 nc:1 nu:0
> [ 29.127699] gandalf kernel: dyndbg: class-ref: drm_kms_helper.DRM_UT_DRIVER module:drm_kms_helper nd:93 nc:0 nu:1
> [ 29.127701] gandalf kernel: dyndbg: class-ref: drm_display_helper.DRM_UT_DRIVER module:drm_display_helper nd:151 nc:0 nu:1
> [ 29.127885] gandalf kernel: dyndbg: class-ref: amdgpu.DRM_UT_DRIVER module:amdgpu nd:4754 nc:0 nu:1
> [ 29.152925] gandalf kernel: dyndbg: processed 1 queries, with 1384 matches, 0 errs
>
>
> The resulting journal is ~14.6k lines, written in the 1st 15 (29)
> seconds of startup. I'm unsure what the 15/29 discrepancy might
> indicate/betray, besides a lot of logging work. sleep 15 is not the
> best stopwatch.
>
> Recent spins thru lkp-test have also been SUCCESS-ful.
>
> CC: Lukas Bartosik <ukaszb@xxxxxxxxxxxx>
> CC: Kees Cook <keescook@xxxxxxxxxxxx> # recent selftests/ reviews
>
> Jim Cromie (33):
>
> cleanups & preparations:
> 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
>
> core fix & selftests:
> dyndbg-API: fix DECLARE_DYNDBG_CLASSMAP
> selftests-dyndbg: add tools/testing/selftests/dynamic_debug/*
> selftests-dyndbg: exit 127 if no facility
> 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 multi-cmds on module classes
> docs/dyndbg: explain new delimiters: comma, percent
> selftests-dyndbg: add test_mod_submod
> selftests-dyndbg: test dyndbg-to-tracefs
> dyndbg-doc: explain flags parse 1st
>
> DRM parts
> drm+drivers: adapt to use DYNDBG_CLASSMAP_{DEFINE,USE}
> drm-dyndbg: adapt to use DYNDBG_CLASSMAP_PARAM
> 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
> drm-print: workaround compiler meh
>
> .../admin-guide/dynamic-debug-howto.rst | 99 ++-
> 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/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 | 10 +
> include/linux/dynamic_debug.h | 127 ++-
> kernel/module/main.c | 3 +
> lib/Kconfig.debug | 24 +-
> lib/Makefile | 3 +
> lib/dynamic_debug.c | 435 ++++++----
> lib/test_dynamic_debug.c | 131 +--
> lib/test_dynamic_debug_submod.c | 17 +
> tools/testing/selftests/Makefile | 1 +
> .../testing/selftests/dynamic_debug/Makefile | 9 +
> tools/testing/selftests/dynamic_debug/config | 2 +
> .../dynamic_debug/dyndbg_selftest.sh | 765 ++++++++++++++++++
> 31 files changed, 1391 insertions(+), 359 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_selftestsh
>
> --
> 2.45.0
>