A few people have asked for this in the past, and I finally got around to implementing it. What this does is to allow writes into trace_marker to initiate a trigger.
The trace_marker event is described in: tracefs/events/ftrace/print Thus the trigger file is added there: tracefs/events/ftrace/print/trigger As there's already a "hist" file there, everything appears to work just like any other trigger to an event. See the last patch for documentation on how to use the triggers to a trace_marker write. By the way, the patch: tracing: Prevent further users of zero size static arrays in trace events May prevent your kernel from building if you include Xen. You will need to add this patch to make it work. http://lkml.kernel.org/r/[email protected] git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git ftrace/core Head SHA1: a3762cfaa4e4b141aa53d3053f38a9cdd47ea49b Steven Rostedt (VMware) (14): tracing: Do not reference event data in post call triggers tracing: Add __find_event_file() to find event files without restrictions tracing: Have event_trace_init() called by trace_init_tracefs() tracing: Add brackets in ftrace event dynamic arrays tracing: Do not show filter file for ftrace internal events tracing: Add trigger file for trace_markers tracefs/ftrace/print tracing: Have zero size length in filter logic be full string tracing: Prevent further users of zero size static arrays in trace events tracing: Allow histogram triggers to access ftrace internal events tracing: Document trace_marker triggers ftrace/selftest: Have the reset_trigger code be a bit more careful ftrace/selftest: Fix reset_trigger() to handle triggers with filters tracing/selftest: Add selftests to test trace_marker histogram triggers tracing/selftest: Add test to test hist trigger between kernel event and trace_marker ---- Changes since v1: - Fixed comment about length (Masami Hiramatsu) - Added note about ->reg() requiremet (Namhyung Kim) - Added fix for r->len (Yann Ylavic) - Added fixes for reset_trigger in ftrace self test - Added self tests to test the trace_marker triggers Documentation/trace/events.rst | 6 +- Documentation/trace/ftrace.rst | 5 + Documentation/trace/histogram.txt | 546 ++++++++++++++++++++- include/linux/trace_events.h | 3 +- include/trace/trace_events.h | 1 + kernel/trace/trace.c | 19 + kernel/trace/trace.h | 9 +- kernel/trace/trace_entries.h | 6 +- kernel/trace/trace_events.c | 36 +- kernel/trace/trace_events_filter.c | 23 +- kernel/trace/trace_events_hist.c | 2 +- kernel/trace/trace_events_trigger.c | 6 +- kernel/trace/trace_export.c | 9 +- tools/testing/selftests/ftrace/test.d/functions | 23 +- .../trigger/trigger-trace-marker-synthetic.tc | 88 ++++ .../ftrace/test.d/trigger/trigger-trace-marker.tc | 49 ++ 16 files changed, 790 insertions(+), 41 deletions(-) create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic.tc create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker.tc
