hi Jason, Steve, Greg, DRM-folks,
This patchset plumbs debug streams, from dynamic-debug, and from drm.debug, into tracefs. Enabling traffic is done on both source & destination:
# enable at source echo module usbcore +T > /proc/dynamic_debug/control # enable events into tracefs echo 1 > /sys/kernel/tracing/events/dyndbg/enable
# enable at source echo 0x03 > /sys/module/drm/parameters/debug # enable events into tracefs echo 1 > /sys/kernel/tracing/events/drm/enable
This allows selectivity at the sources, and in principle, filtering at tracefs (which is unaddressed, except for arg-passthru).
Here is v11, it differs subsantially from v10:
A: All tracefs action is via 4 new trace-events:
from dyndbg: pr_debug() sends trace_prdbg() dev_dbg() sends trace_devdbg() both preserve args unchanged
similarly from drm: drm_dev_dbg() -> trace_drm_devdbg() drm_dbg() -> trace_drm_dbg() again, args are captured unchanged. for some reason 3 other drm_vblank* events showed up, I dont know why.
These 4 events (not counting vblank) all capture the args unchanged; ISTM full exposure of available info is best for filtering/triggering purposes.
B: dynamic-debug gets proper .class_id, and query support (dyndbg:)
so that this is legal input:
echo module drm class 3 +T > /proc/dynamic_debug/control
v10 used "format drm:core:", which worked, but required addition of category string prefixes, and possible user-facing-changes issues.
New field is uint:4, big enough to fit DRMs enum drm_debug_category (once it has been condensed). The name is .class_id, distinct from but related to DRMs "category".
This also includes _CLS name & arg extensions of the Factory macros that implement dyndbgs jump-label/NOOP optimizations.
C: integration of dyndbg into drm.debug (drm_print:)
The purpose here (and originally) is to avoid drm_debug_enabled() runtime costs, and to put a more flexible substrate underneath the sysfs bitmap api. Ive made it CONFIG dependent, since each _ddebug is 56 bytes, and i915 & amdgpu have ~1700 & ~3800 callsites respectively, of which 127 & ~2k are plain pr_debugs.
1. We shrink enum drm_debug_category to fit in 4 bits, at nominal cost of BIT(category) at runtime, which dyndbg will avoid anyway.
2. Add the trace_drm_*dbg() events
3. insert macro indirection, and use it to wrap drm_*dbg()s in dyndbg's _no_desc_ Factory macro.
4. add __drm_debug_enabled (optimized to true) to use behind jumplabel.
5. use _CLS extension of _no_desc_ Factory macro this makes cls available to initialize _ddebug.class_id
6. alter drm_*dbg, replacing category with struct _ddebug *desc. desc.class_id is category desc.flags allows selection of PRINTK or TRACE or both
7. propagate struct _ddebug *desc thru trace_drm_*dbg() make all of _ddebug available for filtering
8. add sysfs bitmap to dyndbg, use it to implement drm.debug
D: The "flight-recorder" special instance was unneeded, and is gone:
this handles it generically:
mkdir instances/flightrec echo 1 > instances/flightrec/events/drm/enable echo module autopilot +T >/proc/dynamic_debug/control
v10 is here: https://lore.kernel.org/lkml/20211105192637.2370737-1-jim.cromie@gmail.com/
patches 1-3 are from: https://lore.kernel.org/lkml/20200721141105.16034-1-vincent.whitchurch@axis....
this patchset addresses goals of: https://patchwork.freedesktop.org/series/78133/ https://lore.kernel.org/lkml/3706af20bc64a320ff8f3ff8950738b988f4bdf5.163645...
Jim Cromie (19):
1st 3 are basically direct from vincent.whitchurch@axis.com execpt I dropped his printk:dyndbg event: dyndbg: add _DPRINTK_FLAGS_ENABLED dyndbg: add _DPRINTK_FLAGS_TRACE dyndbg: add write-to-tracefs code
add 2 events, and record args (could be squashed) dyndbg: add trace-events for pr_debug, dev_dbg dyndbg: add desc, dev fields to event record
add field, selection mechanisms, and CLS extensions to Factory macros dyndbg: add class_id to callsites
make category fit in .class_id: drm_print: condense enum drm_debug_category
repeat trace event addition: drm_print: add trace_drm_dbg, trace_drm_devdbg events
kconfig+Make-flag: drm_print: add CONFIG_DRM_USE_DYNDBG
macro indirection: drm_print: interpose drm_dev_dbg, __drm_dbg with forwarding macros
add >control entries for ~4660 drm.debug callsites: drm_print: wrap drm_dev_dbg in _dynamic_func_call_no_desc drm_print: wrap drm_dbg in _dynamic_func_call_no_desc
prep: drm_print: refine drm_debug_enabled for dyndbg+jump-label
drive-by: drm_print: prefer bare printk KERN_DEBUG on generic fn
get .class_id initialized at compile. drm_print: use _dynamic_func_call_no_desc_cls
need this to selectively trace/print: drm_print: add struct _ddebug desc to drm_dbg, drm_dev_dbg
propagate arg upgrade of HEAD~1 into trace-events: drm_print: add struct _ddebug *desc to trace-drm-*() params
add and use sysfs bitmap support: dyndbg: add DEFINE_DYNAMIC_DEBUG_CLASSBITS macro and callbacks drm_print: use DEFINE_DYNAMIC_DEBUG_CLASSBITS for drm.debug
.../admin-guide/dynamic-debug-howto.rst | 12 + drivers/gpu/drm/Kconfig | 12 + drivers/gpu/drm/drm_print.c | 66 +++-- include/drm/drm_print.h | 80 +++-- include/linux/dynamic_debug.h | 101 ++++++- include/trace/events/drm.h | 68 +++++ include/trace/events/dyndbg.h | 74 +++++ lib/dynamic_debug.c | 273 +++++++++++++++--- 8 files changed, 601 insertions(+), 85 deletions(-) create mode 100644 include/trace/events/drm.h create mode 100644 include/trace/events/dyndbg.h