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
--
2.38.1
