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[PATCH 10/32] tracing: Add NO_DISCARD event file flag

From Tom Zanussi <tom.zanussi@linux.intel.com>
Newsgroups linux.kernel
Subject [PATCH 10/32] tracing: Add NO_DISCARD event file flag
Date 2017-06-27 01:00 +0200
Message-ID <tWL97-8u4-7@gated-at.bofh.it> (permalink)
References <tWKZs-8nP-19@gated-at.bofh.it>
Organization linux.* mail to news gateway

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Whenever an event_command has a post-trigger that needs access to the
event record, the event record can't be discarded, or the post-trigger
will eventually see bogus data.

In order to allow the discard check to treat this case separately, add
an EVENT_FILE_FL_NO_DISCARD flag to the event file flags, along with
code in the discard check that checks the flag and avoids the discard
when the flag is set.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 include/linux/trace_events.h        |  3 +++
 kernel/trace/trace.h                | 13 ++++++++++---
 kernel/trace/trace_events_trigger.c | 16 +++++++++++++---
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index f333114..d7b230b 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -297,6 +297,7 @@ enum {
 	EVENT_FILE_FL_TRIGGER_MODE_BIT,
 	EVENT_FILE_FL_TRIGGER_COND_BIT,
 	EVENT_FILE_FL_PID_FILTER_BIT,
+	EVENT_FILE_FL_NO_DISCARD_BIT,
 };
 
 /*
@@ -311,6 +312,7 @@ enum {
  *  TRIGGER_MODE  - When set, invoke the triggers associated with the event
  *  TRIGGER_COND  - When set, one or more triggers has an associated filter
  *  PID_FILTER    - When set, the event is filtered based on pid
+ *  NO_DISCARD    - When set, do not discard events, something needs them later
  */
 enum {
 	EVENT_FILE_FL_ENABLED		= (1 << EVENT_FILE_FL_ENABLED_BIT),
@@ -322,6 +324,7 @@ enum {
 	EVENT_FILE_FL_TRIGGER_MODE	= (1 << EVENT_FILE_FL_TRIGGER_MODE_BIT),
 	EVENT_FILE_FL_TRIGGER_COND	= (1 << EVENT_FILE_FL_TRIGGER_COND_BIT),
 	EVENT_FILE_FL_PID_FILTER	= (1 << EVENT_FILE_FL_PID_FILTER_BIT),
+	EVENT_FILE_FL_NO_DISCARD	= (1 << EVENT_FILE_FL_NO_DISCARD_BIT),
 };
 
 struct trace_event_file {
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 78c7694..81b1d07 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1271,9 +1271,16 @@ static inline void trace_buffer_unlock_commit(struct trace_array *tr,
 	if (eflags & EVENT_FILE_FL_TRIGGER_COND)
 		*tt = event_triggers_call(file, entry, event);
 
-	if (test_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags) ||
-	    (unlikely(file->flags & EVENT_FILE_FL_FILTERED) &&
-	     !filter_match_preds(file->filter, entry))) {
+	if (unlikely(file->flags & EVENT_FILE_FL_FILTERED) &&
+	    !filter_match_preds(file->filter, entry)) {
+		__trace_event_discard_commit(buffer, event);
+		return true;
+	}
+
+	if (test_bit(EVENT_FILE_FL_NO_DISCARD_BIT, &file->flags))
+		return false;
+
+	if (test_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags)) {
 		__trace_event_discard_commit(buffer, event);
 		return true;
 	}
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 9b0fe31..d345820 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -505,20 +505,30 @@ int trace_event_trigger_enable_disable(struct trace_event_file *file,
 void update_cond_flag(struct trace_event_file *file)
 {
 	struct event_trigger_data *data;
-	bool set_cond = false;
+	bool set_cond = false, set_no_discard = false;
 
 	list_for_each_entry_rcu(data, &file->triggers, list) {
 		if (data->filter || event_command_post_trigger(data->cmd_ops) ||
-		    event_command_needs_rec(data->cmd_ops)) {
+		    event_command_needs_rec(data->cmd_ops))
 			set_cond = true;
+
+		if (event_command_post_trigger(data->cmd_ops) &&
+		    event_command_needs_rec(data->cmd_ops))
+			set_no_discard = true;
+
+		if (set_cond && set_no_discard)
 			break;
-		}
 	}
 
 	if (set_cond)
 		set_bit(EVENT_FILE_FL_TRIGGER_COND_BIT, &file->flags);
 	else
 		clear_bit(EVENT_FILE_FL_TRIGGER_COND_BIT, &file->flags);
+
+	if (set_no_discard)
+		set_bit(EVENT_FILE_FL_NO_DISCARD_BIT, &file->flags);
+	else
+		clear_bit(EVENT_FILE_FL_NO_DISCARD_BIT, &file->flags);
 }
 
 /**
-- 
1.9.3

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Thread

[PATCH 00/32]  tracing: Inter-event (e.g. latency) support Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 00:50 +0200
  [PATCH 17/32] tracing: Account for variables in named trigger compatibility Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 02/32] tracing: Reimplement log2 Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 10/32] tracing: Add NO_DISCARD event file flag Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 11/32] tracing: Add post-trigger flag to hist trigger command Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 19/32] tracing: Add variable reference handling to hist triggers Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 29/32] tracing: Add 'last error' error facility for hist triggers Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 04/32] ring-buffer: Redefine the unimplemented RINGBUF_TIME_TIME_STAMP Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
    Re: [PATCH 04/32] ring-buffer: Redefine the unimplemented RINGBUF_TIME_TIME_STAMP "Joel Fernandes (Google)" <joel.opensrc@gmail.com> - 2017-07-02 11:00 +0200
  [PATCH 06/32] tracing: Add ring buffer event param to hist field functions Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 16/32] tracing: Add variable support to hist triggers Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 20/32] tracing: Add support for dynamic tracepoints Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 24/32] tracing: Add 'onmax' hist trigger action support Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 03/32] ring-buffer: Add interface for setting absolute time stamps Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 13/32] tracing: Add per-element variable support to tracing_map Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 09/32] tracing: Make traceprobe parsing code reusable Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 28/32] tracing: Add hist trigger support for variable reference aliases Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 32/32] tracing: Add a clock attribute for hist triggers Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 25/32] tracing: Allow whitespace to surround hist trigger filter Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 05/32] tracing: Give event triggers access to ring_buffer_event Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 21/32] tracing: Add hist trigger action hook Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 07/32] tracing: Increase tracing map KEYS_MAX size Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 30/32] tracing: Add inter-event hist trigger Documentation Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 31/32] tracing: Make tracing_set_clock() non-static Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 22/32] tracing: Add support for 'synthetic' events Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 12/32] tracing: Add hist trigger timestamp support Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 18/32] tracing: Add simple expression support to hist triggers Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 08/32] tracing: Break out hist trigger assignment parsing Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 15/32] tracing: Add usecs modifier for hist trigger timestamps Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 23/32] tracing: Add 'onmatch' hist trigger action support Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 14/32] tracing: Add hist_data member to hist_field Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 26/32] tracing: Make duplicate count from tracing_map available Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 01/32] tracing: Add hist_field_name() accessor Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  [PATCH 27/32] tracing: Add cpu field for hist triggers Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-27 01:00 +0200
  Re: [PATCH 00/32]  tracing: Inter-event (e.g. latency) support Steven Rostedt <rostedt@goodmis.org> - 2017-06-27 17:10 +0200
  Re: [PATCH 00/32]  tracing: Inter-event (e.g. latency) support Masami Hiramatsu <mhiramat@kernel.org> - 2017-06-28 16:30 +0200
    Re: [PATCH 00/32]  tracing: Inter-event (e.g. latency) support Tom Zanussi <tom.zanussi@linux.intel.com> - 2017-06-28 21:20 +0200
  Re: [PATCH 00/32] tracing: Inter-event (e.g. latency) support "Joel Fernandes (Google)" <joel.opensrc@gmail.com> - 2017-07-01 09:10 +0200

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