From: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Last April, I posted an RFC patchset [1] implementing a common
error_log interface as suggested by Masami [2]. We were supposed to
discuss it at Plumbers but that never happened, and Steve recently
asked about patches for a follow-on discussion [3], so here they are.
I incorporated comments from the previous discussion, the most
important of which are:
- Incorporated Steve's suggestion of using static strings as in the
existing trace event filter code, along with err_info indexing into
the string arrays and a position for the error caret.
- Converted all the hist trigger errors and the existing trace event
filter parse errors to use the new interface.
- Converted a few kprobe_event errors to the new interface as
examples, but these will require more work - I didn't spend much
time figuring out how to get the full kprobe command into the error
info, for instance.
- Got rid of the custom single-page ring buffer and used standard
lists instead.
For now, this is implemented on top of the latest 'hist trigger
snapshot and onchange additions' patchset [4].
Below is an example session of a few failed commands and the
corresponding error_log contents:
# echo > /sys/kernel/debug/tracing/error_log
# echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
# echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
-su: echo: write error: Invalid argument
# cat /sys/kernel/debug/tracing/error_log
hist:sched:sched_wakeup: error: Variable already defined
Command: keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"
^
# echo 'hist:key=comm:p=prio:onchange($q).snapshot()' > /sys/kernel/debug/tracing/events/sched/sched_waking/trigger
-su: echo: write error: Invalid argument
# cat /sys/kernel/debug/tracing/error_log
hist:sched:sched_wakeup: error: Variable already defined
Command: keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"
^
hist:sched:sched_waking: error: Couldn't find onmax or onchange variable
Command: key=comm:p=prio:onchange($q).snapshot()
^
# echo 'hist:keys=pid' >> /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
# echo 'hist:keys=pid' >> /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
-su: echo: write error: File exists
# echo 'comm="cyclictest"' > /sys/kernel/debug/tracing/events/sched/sched_wakeup/filter
-su: echo: write error: Invalid argument
# cat /sys/kernel/debug/tracing/error_log
hist:sched:sched_wakeup: error: Variable already defined
Command: keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"
^
hist:sched:sched_waking: error: Couldn't find onmax or onchange variable
Command: key=comm:p=prio:onchange($q).snapshot()
^
hist:sched:sched_wakeup: error: Hist trigger already exists
Command: keys=pid
^
event filter parse error: error: Invalid operator
Command: comm="cyclictest"
^
# echo "((sig >= 10 && sig < 15) || dsig == 17) && comm != bash" > /sys/kernel/debug/tracing/events/signal/signal_generate/filter
-su: echo: write error: Invalid argument
# cat /sys/kernel/debug/tracing/error_log
hist:sched:sched_wakeup: error: Variable already defined
Command: keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"
^
hist:sched:sched_waking: error: Couldn't find onmax or onchange variable
Command: key=comm:p=prio:onchange($q).snapshot()
^
hist:sched:sched_wakeup: error: Hist trigger already exists
Command: keys=pid
^
event filter parse error: error: Invalid operator
Command: comm="cyclictest"
^
event filter parse error: error: Field not found
Command: ((sig >= 10 && sig < 15) || dsig == 17) && comm != bash
^
Thanks,
Tom
[1] https://lore.kernel.org/lkml/cover.1523545519.git.tom.zanussi@xxxxxxxxxxxxxxx/
[2] https://lore.kernel.org/lkml/20180406105309.b50ea1a21d2cbd9b0e39dbfd@xxxxxxxxxx/
[3] https://lore.kernel.org/lkml/e885d1fd02e76f121d6cc2bb28e58b523e2434a7.camel@xxxxxxxxxxxxxxx/
[4] https://lore.kernel.org/lkml/cover.1549403369.git.tom.zanussi@xxxxxxxxxxxxxxx/
The following changes since commit 779474478eacb64a1e686a37cf663d8210d88f84:
tracing: Add hist trigger action 'expected fail' test case (2019-02-05 14:53:54 -0600)
are available in the git repository at:
git://git.kernel.org/pub/scm/linux/kernel/git/zanussi/linux-trace.git ftrace/error_log_v2
Tom Zanussi (5):
tracing: Add tracing error log
tracing: Save the last hist command's associated event name
tracing: Use tracing error_log with hist triggers
tracing: Use tracing error_log with kprobe events (incomplete)
tracing: Use tracing error_log with trace event filters
kernel/trace/trace.c | 217 ++++++++++++++++++++++++++++++++++++
kernel/trace/trace.h | 4 +
kernel/trace/trace_events_filter.c | 7 +-
kernel/trace/trace_events_hist.c | 221 ++++++++++++++++++++-----------------
kernel/trace/trace_probe.c | 24 +++-
5 files changed, 368 insertions(+), 105 deletions(-)
--
2.14.1
