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| author | Tom Zanussi <tom.zanussi@linux.intel.com> | 2019-04-01 01:48:24 +0200 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-04-08 15:22:50 +0200 |
| commit | 26a944917989d57c0dddec284b3088fa31127717 (patch) | |
| tree | f00b6bbbc91e2b7634d8bc6c44574faf2cbd9a93 /Documentation/trace | |
| parent | selftests/ftrace: Add tracing/error_log testcase (diff) | |
| download | linux-26a944917989d57c0dddec284b3088fa31127717.tar.xz linux-26a944917989d57c0dddec284b3088fa31127717.zip | |
tracing: Add tracing/error_log Documentation
Move most of the hist trigger extended error documentation to
ftrace.rst and expand on it to fully document tracing/error_log.
Link: http://lkml.kernel.org/r/c5d53c8f643ef6844d6ad8d0200c116936730b01.1554072478.git.tom.zanussi@linux.intel.com
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/ftrace.rst | 31 | ||||
| -rw-r--r-- | Documentation/trace/histogram.rst | 16 |
2 files changed, 33 insertions, 14 deletions
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 7c5e6d6ab5d1..809b39d066ee 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -765,6 +765,37 @@ Here is the list of current tracers that may be configured. tracers from tracing simply echo "nop" into current_tracer. +Error conditions +---------------- + + For most ftrace commands, failure modes are obvious and communicated + using standard return codes. + + For other more involved commands, extended error information may be + available via the tracing/error_log file. For the commands that + support it, reading the tracing/error_log file after an error will + display more detailed information about what went wrong, if + information is available. The tracing/error_log file is a circular + error log displaying a small number (currently, 8) of ftrace errors + for the last (8) failed commands. + + The extended error information and usage takes the form shown in + this example:: + + # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger + echo: write error: Invalid argument + + # cat /sys/kernel/debug/tracing/error_log + [ 5348.887237] location: error: Couldn't yyy: zzz + Command: xxx + ^ + [ 7517.023364] location: error: Bad rrr: sss + Command: ppp qqq + ^ + + To clear the error log, echo the empty string into it:: + + # echo > /sys/kernel/debug/tracing/error_log Examples of using the tracer ---------------------------- diff --git a/Documentation/trace/histogram.rst b/Documentation/trace/histogram.rst index 0ea59d45aef1..7612c7ad5715 100644 --- a/Documentation/trace/histogram.rst +++ b/Documentation/trace/histogram.rst @@ -199,20 +199,8 @@ Extended error information For some error conditions encountered when invoking a hist trigger command, extended error information is available via the - corresponding event's 'hist' file. Reading the hist file after an - error will display more detailed information about what went wrong, - if information is available. This extended error information will - be available until the next hist trigger command for that event. - - If available for a given error condition, the extended error - information and usage takes the following form:: - - # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger - echo: write error: Invalid argument - - # cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist - ERROR: Couldn't yyy: zzz - Last command: xxx + tracing/error_log file. See Error Conditions in + :file:`Documentation/trace/ftrace.rst` for details. 6.2 'hist' trigger examples --------------------------- |