From: Sean Paul seanpaul@chromium.org
*Record scratch* You read that subject correctly, I bet you're wondering how we got here. At least hear me out before you flame :-)
For a long while now, we (ChromeOS) have been struggling getting any value out of user feedback reports of display failures (notably external displays not working). The problem is that all logging, even fatal errors (well, fatal in the sense that a display won't light up) are logged at DEBUG log level. So in order to extract these logs, you need to be able to turn on logging, and reproduce the issue with debug enabled. Unfortunately, this isn't really something we can ask CrOS users I spoke with airlied about this and RHEL has similar issues.
This is the point where you ask me, "So Sean, why don't you just enable DRM_UT_BLAH?". Good question! Here are the reasons in ascending order of severity: 1- People aren't consistent with their categories, so we'd have to enable a bunch to get proper coverage 2- We don't want to overwhelm syslog with drm spam, others have to use it too 3- Console logging is slow
Hopefully you're with me so far. I have a problem that has no existing solution. What I really want is a ringbuffer of the most recent logs (in the categories I'm interested in) exposed via debugfs so I can extract it when users file feedback.
It just so happens that there is something which does _exactly_ this! I can dump the most recent logs into tracepoints, turn them on and off depending on which category I want, and pull them from debugfs on demand.
"What about trace_printk()?" You'll say. It doesn't give us the control we get from using tracepoints and it's not meant to be left sprinkled around in code.
So that is how we got here, now it's time for you to tell me why this is a horrible idea :-)
Cc: David Airlie airlied@gmail.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Sean Paul seanpaul@chromium.org --- drivers/gpu/drm/drm_print.c | 143 ++++++++++++++++++++++++++----- include/trace/events/drm_print.h | 116 +++++++++++++++++++++++++ 2 files changed, 239 insertions(+), 20 deletions(-) create mode 100644 include/trace/events/drm_print.h
diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c index 9a25d73c155c..f591292811aa 100644 --- a/drivers/gpu/drm/drm_print.c +++ b/drivers/gpu/drm/drm_print.c @@ -27,11 +27,15 @@
#include <stdarg.h>
+#include <linux/bitops.h> #include <linux/io.h> #include <linux/moduleparam.h> #include <linux/seq_file.h> #include <linux/slab.h>
+#define CREATE_TRACE_POINTS +#include <trace/events/drm_print.h> + #include <drm/drm.h> #include <drm/drm_drv.h> #include <drm/drm_print.h> @@ -241,10 +245,10 @@ void drm_dev_printk(const struct device *dev, const char *level, struct va_format vaf; va_list args;
- va_start(args, format); vaf.fmt = format; vaf.va = &args;
+ va_start(args, format); if (dev) dev_printk(level, dev, "[" DRM_NAME ":%ps] %pV", __builtin_return_address(0), &vaf); @@ -253,49 +257,145 @@ void drm_dev_printk(const struct device *dev, const char *level, level, __builtin_return_address(0), &vaf);
va_end(args); + + va_start(args, format); + trace_drm_log(level, dev, &vaf); + va_end(args); } EXPORT_SYMBOL(drm_dev_printk);
+static unsigned int drm_trace_enabled(unsigned int category) +{ + unsigned int bit; + + for_each_set_bit(bit, (unsigned long*)&category, sizeof(category) * 8) { + switch (BIT(bit)) { + case DRM_UT_NONE: + return trace_drm_dbg_none_enabled(); + case DRM_UT_CORE: + return trace_drm_dbg_core_enabled(); + case DRM_UT_DRIVER: + return trace_drm_dbg_driver_enabled(); + case DRM_UT_KMS: + return trace_drm_dbg_kms_enabled(); + case DRM_UT_PRIME: + return trace_drm_dbg_prime_enabled(); + case DRM_UT_ATOMIC: + return trace_drm_dbg_atomic_enabled(); + case DRM_UT_VBL: + return trace_drm_dbg_vbl_enabled(); + case DRM_UT_STATE: + return trace_drm_dbg_state_enabled(); + case DRM_UT_LEASE: + return trace_drm_dbg_lease_enabled(); + case DRM_UT_DP: + return trace_drm_dbg_dp_enabled(); + default: + return trace_drm_dbg_unknown_enabled(); + } + } + return false; +} + +static void drm_do_trace(const struct device *dev, unsigned int category, + struct va_format *vaf) +{ + WARN_ON(hweight32(category) > 1); + + switch (category) { + case DRM_UT_NONE: + trace_drm_dbg_none(dev, vaf); + break; + case DRM_UT_CORE: + trace_drm_dbg_core(dev, vaf); + break; + case DRM_UT_DRIVER: + trace_drm_dbg_driver(dev, vaf); + break; + case DRM_UT_KMS: + trace_drm_dbg_kms(dev, vaf); + break; + case DRM_UT_PRIME: + trace_drm_dbg_prime(dev, vaf); + break; + case DRM_UT_ATOMIC: + trace_drm_dbg_atomic(dev, vaf); + break; + case DRM_UT_VBL: + trace_drm_dbg_vbl(dev, vaf); + break; + case DRM_UT_STATE: + trace_drm_dbg_state(dev, vaf); + break; + case DRM_UT_LEASE: + trace_drm_dbg_lease(dev, vaf); + break; + case DRM_UT_DP: + trace_drm_dbg_dp(dev, vaf); + break; + default: + trace_drm_dbg_unknown(dev, vaf); + break; + } +} + void drm_dev_dbg(const struct device *dev, unsigned int category, const char *format, ...) { struct va_format vaf; + unsigned int bit; va_list args;
- if (!drm_debug_enabled(category)) - return; - - va_start(args, format); vaf.fmt = format; vaf.va = &args;
- if (dev) - dev_printk(KERN_DEBUG, dev, "[" DRM_NAME ":%ps] %pV", - __builtin_return_address(0), &vaf); - else - printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", - __builtin_return_address(0), &vaf); + if (drm_debug_enabled(category)) { + va_start(args, format); + if (dev) + dev_printk(KERN_DEBUG, dev, "[" DRM_NAME ":%ps] %pV", + __builtin_return_address(0), &vaf); + else + printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", + __builtin_return_address(0), &vaf); + va_end(args); + } + + if (!drm_trace_enabled(category)) + return; + + for_each_set_bit(bit, (unsigned long*)&category, sizeof(category) * 8) { + va_start(args, format); + drm_do_trace(dev, BIT(bit), &vaf); + va_end(args); + }
- va_end(args); } EXPORT_SYMBOL(drm_dev_dbg);
void drm_dbg(unsigned int category, const char *format, ...) { struct va_format vaf; + unsigned int bit; va_list args;
- if (!drm_debug_enabled(category)) - return; - - va_start(args, format); vaf.fmt = format; vaf.va = &args;
- printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", - __builtin_return_address(0), &vaf); + if (drm_debug_enabled(category)) { + va_start(args, format); + printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", + __builtin_return_address(0), &vaf); + va_end(args); + }
- va_end(args); + if (!drm_trace_enabled(category)) + return; + + for_each_set_bit(bit, (unsigned long*)&category, sizeof(category) * 8) { + va_start(args, format); + drm_do_trace(NULL, BIT(bit), &vaf); + va_end(args); + } } EXPORT_SYMBOL(drm_dbg);
@@ -304,13 +404,16 @@ void drm_err(const char *format, ...) struct va_format vaf; va_list args;
- va_start(args, format); vaf.fmt = format; vaf.va = &args;
+ va_start(args, format); printk(KERN_ERR "[" DRM_NAME ":%ps] *ERROR* %pV", __builtin_return_address(0), &vaf); + va_end(args);
+ va_start(args, format); + trace_drm_err(NULL, &vaf); va_end(args); } EXPORT_SYMBOL(drm_err); diff --git a/include/trace/events/drm_print.h b/include/trace/events/drm_print.h new file mode 100644 index 000000000000..cc93c69f3fe4 --- /dev/null +++ b/include/trace/events/drm_print.h @@ -0,0 +1,116 @@ +// SPDX-License-Identifier: MIT +/* + * Copyright (C) 2019 Google, Inc. + * + * Authors: + * Sean Paul seanpaul@chromium.org + */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM drm_print + +#if !defined(_TRACE_DRM_PRINT_H) || defined(TRACE_HEADER_MULTI_READ) + +#include <linux/device.h> +#include <linux/tracepoint.h> + +#define DRM_PRINT_MAX 256 + +#define _TRACE_DRM_PRINT_H + +TRACE_EVENT(drm_log, + TP_PROTO(const char * level, const struct device *dev, + struct va_format *vaf), + TP_ARGS(level, dev, vaf), + TP_STRUCT__entry( + __field(const char *, level ) + __field(const struct device *, dev ) + __dynamic_array(char, msg, DRM_PRINT_MAX ) + __field(int, len ) + ), + TP_fast_assign( + __entry->level = level; + __entry->dev = dev; + __entry->len = vsnprintf(__get_str(msg), DRM_PRINT_MAX, + vaf->fmt, *vaf->va); + if (__entry->len > 0 && + __get_str(msg)[__entry->len - 1] == '\n') + __get_str(msg)[--__entry->len] = '\0'; + ), + TP_printk("%s %s %s: %s", __entry->level, + __entry->dev ? dev_driver_string(__entry->dev) : "(NULL):", + __entry->dev ? dev_name(__entry->dev) : "", __get_str(msg)) +); + +TRACE_EVENT(class_drm_category_log, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf), + TP_STRUCT__entry( + __field(const struct device *, dev ) + __dynamic_array(char, msg, DRM_PRINT_MAX ) + __field(int, len ) + ), + TP_fast_assign( + __entry->dev = dev; + __entry->len = vsnprintf(__get_str(msg), DRM_PRINT_MAX, + vaf->fmt, *vaf->va); + if (__entry->len > 0 && + __get_str(msg)[__entry->len - 1] == '\n') + __get_str(msg)[--__entry->len] = '\0'; + ), + TP_printk("%s %s%s%s", + __entry->dev ? dev_driver_string(__entry->dev) : "", + __entry->dev ? dev_name(__entry->dev) : "", + __entry->dev ? ": " : "", __get_str(msg)) +); +DEFINE_EVENT(class_drm_category_log, drm_err, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf) +); +DEFINE_EVENT(class_drm_category_log, drm_dbg_none, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf) +); +DEFINE_EVENT(class_drm_category_log, drm_dbg_core, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf) +); +DEFINE_EVENT(class_drm_category_log, drm_dbg_driver, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf) +); +DEFINE_EVENT(class_drm_category_log, drm_dbg_kms, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf) +); +DEFINE_EVENT(class_drm_category_log, drm_dbg_prime, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf) +); +DEFINE_EVENT(class_drm_category_log, drm_dbg_atomic, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf) +); +DEFINE_EVENT(class_drm_category_log, drm_dbg_vbl, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf) +); +DEFINE_EVENT(class_drm_category_log, drm_dbg_state, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf) +); +DEFINE_EVENT(class_drm_category_log, drm_dbg_lease, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf) +); +DEFINE_EVENT(class_drm_category_log, drm_dbg_dp, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf) +); +DEFINE_EVENT(class_drm_category_log, drm_dbg_unknown, + TP_PROTO(const struct device *dev, struct va_format *vaf), + TP_ARGS(dev, vaf) +); +#endif + +/* This part must be outside protection */ +#include <trace/define_trace.h>