In order to use dynamic-debug's jump-label optimization in drm-debug,
its clarifying to refine drm_debug_enabled into 3 uses:
1. drm_debug_enabled - legacy, public
2. __drm_debug_enabled - optimized for dyndbg jump-label enablement.
3. _drm_debug_enabled - pr_debug instrumented, observable
1. The legacy version always checks the bits.
2. is privileged, for use by __drm_dbg(), __drm_dev_dbg(), which do an
early return unless the category is enabled (free of call/NOOP side
effects). For dyndbg builds, debug callsites are selectively
"pre-enabled", so __drm_debug_enabled() short-circuits to true there.
Remaining callers of 1 may be able to use 2, case by case.
3. is 1st wrapped in a macro, with a pr_debug, which reports each
usage in /proc/dynamic_debug/control, making it observable in the
logs. The macro lets the pr_debug see the real caller, not an inline
function.
When plugged into 1, it identified ~10 remaining callers of the
function, leading to the follow-on cleanup patch, and would allow
activating the pr_debugs, estimating the callrate, and the potential
savings by using the wrapper macro. It is unused ATM, but it fills
out the picture.
Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
drivers/gpu/drm/drm_print.c | 4 ++--
include/drm/drm_print.h | 28 ++++++++++++++++++++++++++++
2 files changed, 30 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
index e45ba224e57c..92e6e18026da 100644
--- a/drivers/gpu/drm/drm_print.c
+++ b/drivers/gpu/drm/drm_print.c
@@ -262,7 +262,7 @@ void __drm_dev_dbg(const struct device *dev, enum drm_debug_category category,
struct va_format vaf;
va_list args;
- if (!drm_debug_enabled(category))
+ if (!__drm_debug_enabled(category))
return;
va_start(args, format);
@@ -285,7 +285,7 @@ void ___drm_dbg(enum drm_debug_category category, const char *format, ...)
struct va_format vaf;
va_list args;
- if (!drm_debug_enabled(category))
+ if (!__drm_debug_enabled(category))
return;
va_start(args, format);
diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h
index 06f0ee06be1f..38ef044d786e 100644
--- a/include/drm/drm_print.h
+++ b/include/drm/drm_print.h
@@ -319,11 +319,39 @@ enum drm_debug_category {
DRM_UT_DRMRES
};
+/*
+ * 3 name flavors of drm_debug_enabled:
+ * drm_debug_enabled - public/legacy, always checks bits
+ * _drm_debug_enabled - instrumented to observe call-rates, est overheads.
+ * __drm_debug_enabled - privileged - knows jump-label state, can short-circuit
+ */
static inline bool drm_debug_enabled(enum drm_debug_category category)
{
return unlikely(__drm_debug & BIT(category));
}
+/*
+ * Wrap fn in macro, so that the pr_debug sees the actual caller, not
+ * the inline fn. Using this name creates a callsite entry / control
+ * point in /proc/dynamic_debug/control.
+ */
+#define _drm_debug_enabled(category) \
+ ({ \
+ pr_debug("todo: maybe avoid via dyndbg\n"); \
+ drm_debug_enabled(category); \
+ })
+
+#if defined(CONFIG_DRM_USE_DYNAMIC_DEBUG)
+/*
+ * dyndbg is wrapping the drm.debug API, so as to avoid the runtime
+ * bit-test overheads of drm_debug_enabled() in those api calls.
+ * In this case, executed callsites are known enabled, so true.
+ */
+#define __drm_debug_enabled(category) true
+#else
+#define __drm_debug_enabled(category) drm_debug_enabled(category)
+#endif
+
/*
* struct device based logging
*
--
2.35.1
