[PATCH v3] drm: Funnel drm logs to tracepoints
Jani Nikula
jani.nikula at linux.intel.com
Fri Dec 13 15:34:25 UTC 2019
On Thu, 12 Dec 2019, Sean Paul <sean at poorly.run> wrote:
> From: Sean Paul <seanpaul at chromium.org>
>
> 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, users 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
> to do. I spoke with airlied about this and RHEL has similar issues. After
> a few more people piped up on previous versions of this patch, it is a
> Real Issue.
>
> So why don't we just enable DRM_UT_BLAH? 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
>
> So what we really want is a ringbuffer of the most recent logs
> (filtered by categories we're interested in) exposed via debugfs so the
> logs can be extracted when users file feedback.
>
> It just so happens that there is something which does _exactly_ this!
> This patch dumps drm logs into tracepoints, which allows us to turn tracing
> on and off depending on which category is useful, and pull them from
> tracefs on demand.
>
> What about trace_printk()? It doesn't give us the control we get from using
> tracepoints and it's not meant to be left sprinkled around in code.
>
> Cc: David Airlie <airlied at gmail.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Pekka Paalanen <ppaalanen at gmail.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Rob Clark <robdclark at gmail.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> Signed-off-by: Sean Paul <seanpaul at chromium.org>
> Link: https://patchwork.freedesktop.org/patch/msgid/20191010204823.195540-1-sean@poorly.run #v1
>
> Changes in v2:
> - Went with a completely different approach: https://lists.freedesktop.org/archives/dri-devel/2019-November/243230.html
>
> Changes in v3:
> - Changed commit message to be a bit less RFC-y
> - Make class_drm_category_log an actual trace class
> ---
>
> Even though we don't want it to be, this is UAPI. So here's some userspace
> code which uses it:
> https://chromium-review.googlesource.com/c/chromiumos/platform2/+/1965562
>
>
> 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) {
You'll want to use BITS_PER_TYPE().
But wait, I've switched category to an enum upstream, and there should
only ever be one bit set anyway?
> + 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)) {
Ville wants to move this check outside of the functions in the macro
level in the header file. Apparently it's pretty bad for performance on
some (older Atom) machines to do the call for nothing.
BR,
Jani.
> + 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..862728fe0f89
> --- /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 at 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))
> +);
> +
> +DECLARE_EVENT_CLASS(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>
--
Jani Nikula, Intel Open Source Graphics Center
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