Merge tag 'trace-v4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:
 "New features:

   - Tom Zanussi's extended histogram work.

     This adds the synthetic events to have histograms from multiple
     event data Adds triggers "onmatch" and "onmax" to call the
     synthetic events Several updates to the histogram code from this

   - Allow way to nest ring buffer calls in the same context

   - Allow absolute time stamps in ring buffer

   - Rewrite of filter code parsing based on Al Viro's suggestions

   - Setting of trace_clock to global if TSC is unstable (on boot)

   - Better OOM handling when allocating large ring buffers

   - Added initcall tracepoints (consolidated initcall_debug code with
     them)

  And other various fixes and clean ups"

* tag 'trace-v4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (68 commits)
  init: Have initcall_debug still work without CONFIG_TRACEPOINTS
  init, tracing: Have printk come through the trace events for initcall_debug
  init, tracing: instrument security and console initcall trace events
  init, tracing: Add initcall trace events
  tracing: Add rcu dereference annotation for test func that touches filter->prog
  tracing: Add rcu dereference annotation for filter->prog
  tracing: Fixup logic inversion on setting trace_global_clock defaults
  tracing: Hide global trace clock from lockdep
  ring-buffer: Add set/clear_current_oom_origin() during allocations
  ring-buffer: Check if memory is available before allocation
  lockdep: Add print_irqtrace_events() to __warn
  vsprintf: Do not preprocess non-dereferenced pointers for bprintf (%px and %pK)
  tracing: Uninitialized variable in create_tracing_map_fields()
  tracing: Make sure variable string fields are NULL-terminated
  tracing: Add action comparisons when testing matching hist triggers
  tracing: Don't add flag strings when displaying variable references
  tracing: Fix display of hist trigger expressions containing timestamps
  ftrace: Drop a VLA in module_exists()
  tracing: Mention trace_clock=global when warning about unstable clocks
  tracing: Default to using trace_global_clock if sched_clock is unstable
  ...

1 files changed, 24 insertions, 0 deletions

diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index fdf5fb54a04c..e45f0786f3f9 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -543,6 +543,30 @@ of ftrace. Here is a list of some of the key files:
 
 	See events.txt for more information.
 
+  timestamp_mode:
+
+	Certain tracers may change the timestamp mode used when
+	logging trace events into the event buffer.  Events with
+	different modes can coexist within a buffer but the mode in
+	effect when an event is logged determines which timestamp mode
+	is used for that event.  The default timestamp mode is
+	'delta'.
+
+	Usual timestamp modes for tracing:
+
+	  # cat timestamp_mode
+	  [delta] absolute
+
+	  The timestamp mode with the square brackets around it is the
+	  one in effect.
+
+	  delta: Default timestamp mode - timestamp is a delta against
+	         a per-buffer timestamp.
+
+	  absolute: The timestamp is a full timestamp, not a delta
+                 against some other value.  As such it takes up more
+                 space and is less efficient.
+
   hwlat_detector:
 
 	Directory for the Hardware Latency Detector.