This patchset has 3 separate but related parts:
1. DEFINE_DYNAMIC_DEBUG_CATEGORIES [patch 1/10]
Declares DRM.debug style bitmap, bits control pr_debugs by matching formats Adds callback to translate bits to $cmd > dynamic_debug/control This could obsolete EXPORT(dynamic_debug_exec_queries) not included.
anticipated_usage: DEFINE_DYNAMIC_DEBUG_CATEGORIES(debug, __drm_debug, " bits control drm.debug categories ", [0] = { DRM_DBG_CAT_CORE }, [1] = { DRM_DBG_CAT_DRIVER }, [2] = { DRM_DBG_CAT_KMS }, [3] = { DRM_DBG_CAT_PRIME }, ...);
2. use (1) to reimplement drm.debug [patches 3-7]::
1st in amdgpu & i915 to control existing pr_debugs by their formats then in drm-print, for all drm.debug API users avoids drm_debug_enabled(), gives NOOP savings & new flexibility. changes drm.debug categories from enum to format-prefix-string alters log format to include the format-prefix-string Daniel Vetter liked this at -v3 https://lore.kernel.org/lkml/YPbPvm%2FxcBlTK1wq@phenom.ffwll.local/ Im sure Ive missed stuff.
3. separately, Sean Paul proposed drm.trace to mirror drm.debug to tracefs https://patchwork.freedesktop.org/series/78133/ ::
He argues:: tracefs is fast/lightweight compared to syslog independent selection means tailored traffic for both
ISTM he's correct. So it follows that its also good for dyndbg, where its then available for all pr_debug users (if CONFIG_TRACING).
So basically, I borg'd his:: [patch 14/14] drm/print: Add tracefs support to the drm logging helpers
Then I added a T flag, so anyone can enable it::
# turn on all drm's pr_debug --> tracefs echo module drm +T > /proc/dynamic_debug/control
It appears to just work: (RFC)
The instance name is purposely crappy, to force a revisit later, maybe "pr_debugs" (plural). Per-module subdirs kinda fits the tracefs pattern, but ./dyndbg-tracefs/$module/$file/$function/$line seems a little like overkill. RFC.
[root@gandalf dyndbg-tracefs]# pwd /sys/kernel/tracing/instances/dyndbg-tracefs [root@gandalf dyndbg-tracefs]# echo 1 > /sys/module/drm/parameters/trace [root@gandalf dyndbg-tracefs]# head -n16 trace | sed -e 's/^#//' tracer: nop
entries-in-buffer/entries-written: 405/405 #P:24
_-----=> irqs-off / _----=> need-resched | / _---=> hardirq/softirq || / _--=> preempt-depth ||| / _-=> migrate-disable |||| / delay TASK-PID CPU# ||||| TIMESTAMP FUNCTION | | | ||||| | | <...>-2254 [000] ..... 7040.894352: __dynamic_pr_debug: drm:core: comm="gnome-shel:cs0" pid=2254, dev=0xe200, auth=1, AMDGPU_CS <...>-2207 [015] ..... 7040.894654: __dynamic_pr_debug: drm:core: comm="gnome-shell" pid=2207, dev=0xe200, auth=1, DRM_IOCTL_MODE_ADDFB2 <...>-2207 [015] ..... 7040.995403: __dynamic_pr_debug: drm:core: comm="gnome-shell" pid=2207, dev=0xe200, auth=1, DRM_IOCTL_MODE_RMFB <...>-2207 [015] ..... 7040.995413: __dynamic_pr_debug: drm:core: OBJ ID: 121 (2)
This is the pr-debug doing most of that logging: (from dynamic_debug/control)
drivers/gpu/drm/drm_ioctl.c:866 [drm]drm_ioctl =T "drm:core: comm=\042%s\042 pid=%d, dev=0x%lx, auth=%d, %s\012"
Turning on decoration flags changes the trace:
echo module drm format drm:core: +mflt > /proc/dynamic_debug/control
TASK-PID CPU# ||||| TIMESTAMP FUNCTION | | | ||||| | | <...>-2254 [003] ..... 15980.936660: __dynamic_pr_debug: [2254] drm:drm_ioctl:866: drm:core: comm="gnome-shel:cs0" pid=2254, dev=0xe200, auth=1, AMDGPU_CS <...>-2207 [015] ..... 15980.936966: __dynamic_pr_debug: [2207] drm:drm_ioctl:866: drm:core: comm="gnome-shell" pid=2207, dev=0xe200, auth=1, DRM_IOCTL_MODE_ADDFB2 <...>-2207 [015] ..... 15981.037727: __dynamic_pr_debug: [2207] drm:drm_ioctl:866: drm:core: comm="gnome-shell" pid=2207, dev=0xe200, auth=1, DRM_IOCTL_MODE_RMFB <...>-2207 [015] ..... 15981.037739: __dynamic_pr_debug: [2207] drm:drm_mode_object_put:195: drm:core: OBJ ID: 124 (2) <...>-2207 [015] ..... 15981.037742: __dynamic_pr_debug: [2207] drm:drm_mode_object_put:195: drm:core: OBJ ID: 124 (1)
The FUNCTION could stand tweaking (to match the callsite in the control file, cited above), or perhaps replaced by the 'mfl' decorations; the 't' flag is redundant for trace. Meh.
SELFTEST
A previous version of this patchset added test_dynamic_debug.ko, but it relied upon code I ripped out when I made tracefs available by default (without modules registering 1st). So it fails 10/29 tests, which counted +T sites executed, via side effect.
TODO: userspace selftest
# to set expected tracing activity echo module test_dynamic_debug function do_debugging +T > control
# run do_debugging function (todo: add sysfs knob) echo 2 > /sys/module/test-dynamic-debug/parameters/do_debugging
If thats wrapped in the right trace_on, trace_pipe, etc incantations, the +T enabled pr_debugs in do_debugging() can be counted, compared against expectations, and passed or failed.
v8 is here: https://patchwork.freedesktop.org/series/93914/ https://lore.kernel.org/lkml/20210915163957.2949166-1-jim.cromie@gmail.com/
The major change since v8 is that +T now works for all users, if CONFIG_TRACING=y, otherwise it complains/errors.
Jim Cromie (10): dyndbg: add DEFINE_DYNAMIC_DEBUG_CATEGORIES macro and callbacks drm: fix doc grammar amdgpu: use dyndbg.CATEGORIES to control existing pr_dbgs i915/gvt: trim spaces from pr_debug "gvt: core:" prefixes i915/gvt: use dyndbg.CATEGORIES for existing pr_debugs drm_print: add choice to use dynamic debug in drm-debug drm_print: instrument drm_debug_enabled dyndbg: add print-to-tracefs, selftest with it - RFC dyndbg: create DEFINE_DYNAMIC_DEBUG_TRACE_CATEGORIES drm: use DEFINE_DYNAMIC_DEBUG_TRACE_CATEGORIES bitmap to tracefs
.../admin-guide/dynamic-debug-howto.rst | 7 +- MAINTAINERS | 1 + drivers/gpu/drm/Kconfig | 26 ++ drivers/gpu/drm/Makefile | 3 + drivers/gpu/drm/amd/amdgpu/Makefile | 2 + .../gpu/drm/amd/display/dc/core/dc_debug.c | 44 +++- drivers/gpu/drm/drm_print.c | 72 ++++-- drivers/gpu/drm/i915/Makefile | 2 + drivers/gpu/drm/i915/gvt/debug.h | 18 +- drivers/gpu/drm/i915/intel_gvt.c | 34 +++ include/drm/drm_drv.h | 2 +- include/drm/drm_print.h | 184 ++++++++++++--- include/linux/dynamic_debug.h | 72 +++++- lib/Kconfig.debug | 11 + lib/Makefile | 1 + lib/dynamic_debug.c | 203 ++++++++++++++-- lib/test_dynamic_debug.c | 222 ++++++++++++++++++ 17 files changed, 815 insertions(+), 89 deletions(-) create mode 100644 lib/test_dynamic_debug.c