[PATCH 2/5] tracing: Make stacktrace trigger affect the correct instance

[Howard Cochran <hcochran@kernelspring.com>]

Currently, the stacktrace trigger always dumps the stack into the top
level buffer, even if it was triggered within an instance. Fixed
by using the trace_array associated with the trace_event_file which
fired the trigger.

Signed-off-by: Howard Cochran <hcochran@kernelspring.com>
---
 kernel/trace/trace.c                | 21 +++++++++++++++++----
 kernel/trace/trace.h                |  2 ++
 kernel/trace/trace_events_trigger.c |  2 +-
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a2f0b9f..5541517 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1900,14 +1900,15 @@ void __trace_stack(struct trace_array *tr, unsigned long flags, int skip,
 }
 
 /**
- * trace_dump_stack - record a stack back trace in the trace buffer
+ * __trace_dump_stack - record a stack back trace in the given trace buffer
  * @skip: Number of functions to skip (helper handlers)
+ * @tr:   Which trace buffer (instance) to write to
  */
-void trace_dump_stack(int skip)
+void __trace_dump_stack(int skip, struct trace_array *tr)
 {
 	unsigned long flags;
 
-	if (tracing_disabled || tracing_selftest_running)
+	if (tracing_disabled || tr->buffer_disabled || tracing_selftest_running)
 		return;
 
 	local_save_flags(flags);
@@ -1917,10 +1918,22 @@ void trace_dump_stack(int skip)
 	 * this function.
 	 */
 	skip += 3;
-	__ftrace_trace_stack(global_trace.trace_buffer.buffer,
+	__ftrace_trace_stack(tr->trace_buffer.buffer,
 			     flags, skip, preempt_count(), NULL);
 }
 
+/**
+ * trace_dump_stack - record a stack back trace in the top-level trace buffer
+ * @skip: Number of functions to skip (helper handlers)
+ */
+void trace_dump_stack(int skip)
+{
+	/* This wrapper function deepens the stack one level */
+	skip += 1;
+
+	__trace_dump_stack(skip, &global_trace);
+}
+
 static DEFINE_PER_CPU(int, user_stack_count);
 
 void
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index ca4915f..00a5419 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -716,6 +716,8 @@ enum print_line_t print_trace_line(struct trace_iterator *iter);
 
 extern char trace_find_mark(unsigned long long duration);
 
+void __trace_dump_stack(int skip, struct trace_array *tr);
+
 /* Standard output formatting function used for function return traces */
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index b69f2a2..adfcd53 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -996,7 +996,7 @@ static void
 stacktrace_trigger(struct event_trigger_data *data, void *rec,
 		   struct trace_event_file *file)
 {
-	trace_dump_stack(STACK_SKIP);
+	__trace_dump_stack(STACK_SKIP, file->tr);
 }
 
 static void
-- 
1.9.1