[PATCH 3.16 225/366] tracing: Fix missing return symbol in function_graph output

[Ben Hutchings]

3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Changbin Du <changbin.du@xxxxxxxxx>

commit 1fe4293f4b8de75824935f8d8e9a99c7fc6873da upstream.

The function_graph tracer does not show the interrupt return marker for the
leaf entry. On leaf entries, we see an unbalanced interrupt marker (the
interrupt was entered, but nevern left).

Before:
 1)               |  SyS_write() {
 1)               |    __fdget_pos() {
 1)   0.061 us    |      __fget_light();
 1)   0.289 us    |    }
 1)               |    vfs_write() {
 1)   0.049 us    |      rw_verify_area();
 1) + 15.424 us   |      __vfs_write();
 1)   ==========> |
 1)   6.003 us    |      smp_apic_timer_interrupt();
 1)   0.055 us    |      __fsnotify_parent();
 1)   0.073 us    |      fsnotify();
 1) + 23.665 us   |    }
 1) + 24.501 us   |  }

After:
 0)               |  SyS_write() {
 0)               |    __fdget_pos() {
 0)   0.052 us    |      __fget_light();
 0)   0.328 us    |    }
 0)               |    vfs_write() {
 0)   0.057 us    |      rw_verify_area();
 0)               |      __vfs_write() {
 0)   ==========> |
 0)   8.548 us    |      smp_apic_timer_interrupt();
 0)   <========== |
 0) + 36.507 us   |      } /* __vfs_write */
 0)   0.049 us    |      __fsnotify_parent();
 0)   0.066 us    |      fsnotify();
 0) + 50.064 us   |    }
 0) + 50.952 us   |  }

Link: http://lkml.kernel.org/r/1517413729-20411-1-git-send-email-changbin.du@xxxxxxxxx

Fixes: f8b755ac8e0cc ("tracing/function-graph-tracer: Output arrows signal on hardirq call/return")
Signed-off-by: Changbin Du <changbin.du@xxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
[bwh: Backported to 3.16: Propagate return of TRACE_TYPE_PARTIAL_LINE from
 print_graph_irq()]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 kernel/trace/trace_functions_graph.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -828,6 +828,7 @@ print_graph_entry_leaf(struct trace_iter
 	struct ftrace_graph_ret *graph_ret;
 	struct ftrace_graph_ent *call;
 	unsigned long long duration;
+	int cpu = iter->cpu;
 	int ret;
 	int i;
 
@@ -837,7 +838,6 @@ print_graph_entry_leaf(struct trace_iter
 
 	if (data) {
 		struct fgraph_cpu_data *cpu_data;
-		int cpu = iter->cpu;
 
 		cpu_data = per_cpu_ptr(data->cpu_data, cpu);
 
@@ -874,6 +874,11 @@ print_graph_entry_leaf(struct trace_iter
 	if (!ret)
 		return TRACE_TYPE_PARTIAL_LINE;
 
+	ret = print_graph_irq(iter, graph_ret->func, TRACE_GRAPH_RET,
+			      cpu, iter->ent->pid, flags);
+	if (ret == TRACE_TYPE_PARTIAL_LINE)
+		return ret;
+
 	return TRACE_TYPE_HANDLED;
 }