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Subject[PATCH v4 00/11] tracing: common error_log for ftrace
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From: Tom Zanussi <tom.zanussi@linux.intel.com>

Hi,

This is v4 of the frace error_log patchset. This version adds
Masami's probe events error_log patches and removes the previous
placeholder for that. It also removes the hist trigger extended error
err testcase and replaces it with a basic error_log functionality
testcase, and replaces the error numbering with timestamps, also as
suggested by Masami. Finally, the Documentation and README are both
updated to describe the error_log.

Note: The probe event error_log test cases failed on my Ubuntu system,
due to the >& redirection operator that dash doesn't understand, so I
tacked on a final patch that fixes it for me. If acceptable, feel
free to just merge it with Masami's patch.

Changes from v3:

- Added Masami's [PATCH 05/11] tracing: Use tracing error_log with probe events
- Added Masami's [PATCH 06/11] selftests/ftrace: Add error_log testcase for probe
- Added [PATCH 11/11] to fix [PATCH 06/11]
- Removed [RFC PATCH v3 4/5] tracing: Use tracing error_log with kprobe events
- Added [PATCH 08/11] selftests/ftrace: Add tracing/error_log testcase
- Removed trigger-extended-error-support testcase
- Changed [n] numbering to [timestamp] numbering as suggested by Masami
- Updated Documentation and README

Changes from v2:

- Added [n] numbering as suggested by Masami


Text from original post:

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
[ 217.431858] 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
[ 217.431858] hist:sched:sched_wakeup: error: Variable already defined
Command: keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"
^
[ 311.554978] 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
[ 217.431858] hist:sched:sched_wakeup: error: Variable already defined
Command: keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"
^
[ 311.554978] hist:sched:sched_waking: error: Couldn't find onmax or onchange variable
Command: key=comm:p=prio:onchange($q).snapshot()
^
[ 715.626153] hist:sched:sched_wakeup: error: Hist trigger already exists
Command: keys=pid
^
[ 730.480310] 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
[ 217.431858] hist:sched:sched_wakeup: error: Variable already defined
Command: keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"
^
[ 311.554978] hist:sched:sched_waking: error: Couldn't find onmax or onchange variable
Command: key=comm:p=prio:onchange($q).snapshot()
^
[ 715.626153] hist:sched:sched_wakeup: error: Hist trigger already exists
Command: keys=pid
^
[ 730.480310] event filter parse error: error: Invalid operator
Command: comm="cyclictest"
^
[ 800.548673] 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@linux.intel.com/
[2] https://lore.kernel.org/lkml/20180406105309.b50ea1a21d2cbd9b0e39dbfd@kernel.org/
[3] https://lore.kernel.org/lkml/e885d1fd02e76f121d6cc2bb28e58b523e2434a7.camel@linux.intel.com/
[4] https://lore.kernel.org/lkml/cover.1549403369.git.tom.zanussi@linux.intel.com/


The following changes since commit a039480e9e93896cadc5a91468964febb3c5d488:

tracing/probe: Verify alloc_trace_*probe() result (2019-03-14 19:54:21 -0400)

are available in the git repository at:

git://git.kernel.org/pub/scm/linux/kernel/git/zanussi/linux-trace.git ftrace/error_log_v4

Masami Hiramatsu (2):
tracing: Use tracing error_log with probe events
selftests/ftrace: Add error_log testcase for probe errors

Tom Zanussi (9):
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 trace event filters
tracing: Remove trigger-extended-error-support testcase
selftests/ftrace: Add tracing/error_log testcase
tracing: Add tracing/error_log Documentation
tracing: Add error_log to README
selftests/ftrace: Change stderr redirection for probe error_log
testcase

Documentation/trace/ftrace.rst | 31 +++
Documentation/trace/histogram.rst | 16 +-
kernel/trace/trace.c | 224 +++++++++++++++++
kernel/trace/trace.h | 4 +
kernel/trace/trace_events_filter.c | 7 +-
kernel/trace/trace_events_hist.c | 221 +++++++++--------
kernel/trace/trace_kprobe.c | 77 +++---
kernel/trace/trace_probe.c | 274 +++++++++++++++------
kernel/trace/trace_probe.h | 77 +++++-
kernel/trace/trace_uprobe.c | 44 +++-
.../ftrace/test.d/ftrace/tracing-error-log.tc | 23 ++
.../ftrace/test.d/kprobe/kprobe_syntax_errors.tc | 93 +++++++
.../ftrace/test.d/kprobe/uprobe_syntax_errors.tc | 31 +++
.../inter-event/trigger-extended-error-support.tc | 28 ---
14 files changed, 883 insertions(+), 267 deletions(-)
create mode 100644 tools/testing/selftests/ftrace/test.d/ftrace/tracing-error-log.tc
create mode 100644 tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
create mode 100644 tools/testing/selftests/ftrace/test.d/kprobe/uprobe_syntax_errors.tc
delete mode 100644 tools/testing/selftests/ftrace/test.d/trigger/inter-event/trigger-extended-error-support.tc

--
2.14.1

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