On Fri, Dec 13, 2019 at 05:34:25PM +0200, Jani Nikula wrote: > On Thu, 12 Dec 2019, Sean Paul <[email protected]> wrote: > > From: Sean Paul <[email protected]> > > > > 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 <[email protected]> > > Cc: Daniel Vetter <[email protected]> > > Cc: Pekka Paalanen <[email protected]> > > Cc: Joonas Lahtinen <[email protected]> > > Cc: Thomas Zimmermann <[email protected]> > > Cc: Rob Clark <[email protected]> > > Cc: Ville Syrjälä <[email protected]> > > Acked-by: Daniel Vetter <[email protected]> > > Signed-off-by: Sean Paul <[email protected]> > > Link: > > https://patchwork.freedesktop.org/patch/msgid/[email protected] > > #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.
I've been meaning to measure if this actually matters. But haven't managed to motivate myself enough. Could be a good project for some random person to write a test that just does tons of different kinds of atomic TEST_ONLY commits to measure how badly we suck. -- Ville Syrjälä Intel _______________________________________________ dri-devel mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/dri-devel
