On Tue, Oct 15, 2019 at 5:07 AM Thomas Zimmermann <tzimmermann@xxxxxxx> wrote:
>
> Hi
>
> Am 10.10.19 um 22:48 schrieb Sean Paul:
> > From: Sean Paul <seanpaul@xxxxxxxxxxxx>
> >
> > *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.
>
> For bug reports, I don't want categories or anything else that users can
> switch on/off. All I'd want is a simple way of retrieving the last ~100
> messages from DRM (ala: "please attach the content of the file at
> /sys/debug...").
>
> > 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 :-)
>
> Tracepoints are considered stable uapi, right? As a distro person (SUSE)
> I don't want us to have to maintain debugging messages forever.
>
it does seem like there is somehow some room for unstable/debug
tracepoints, so we can re-use the tracepoint mechanism for things like
the
BR,
-R
>
> The problem itself doesn't seem related to DRM. Do other subsystems have
> similar requirements?
>
> Best regards
> Thomas
>
> > Cc: David Airlie <airlied@xxxxxxxxx>
> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > Signed-off-by: Sean Paul <seanpaul@xxxxxxxxxxxx>
> > ---
> > 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@xxxxxxxxxxxx>
> > + */
> > +#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>
> >
>
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Felix Imendörffer
>
> _______________________________________________
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> dri-devel@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
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