commit e49dc19c6a19ea112fcb94b7c62ec62cdd5c08aa
author Steven Rostedt <srostedt@redhat.com> Tue Dec 02 23:50:05 2008 -0500
committer Ingo Molnar <mingo@elte.hu> Wed Dec 03 08:56:26 2008 +0100
tree 851dcdfe321e16a327d656ecd7040ef6e8590bec
parent 7ee991fbc6f947e9b04f29c9c6c1d057d0671a16

ftrace: function graph return for function entry

Impact: feature, let entry function decide to trace or not

This patch lets the graph tracer entry function decide if the tracing
should be done at the end as well. This requires all function graph
entry functions return 1 if it should trace, or 0 if the return should
not be traced.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/ftrace.c

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index adba8e9..d278ad2 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -425,6 +425,7 @@
 	trace->calltime = current->ret_stack[index].calltime;
 	trace->overrun = atomic_read(&current->trace_overrun);
 	trace->depth = index;
+	barrier();
 	current->curr_ret_stack--;
 }
 
@@ -506,7 +507,11 @@
 	}
 
 	trace.func = self_addr;
-	ftrace_graph_entry(&trace);
 
+	/* Only trace if the calling function expects to */
+	if (!ftrace_graph_entry(&trace)) {
+		current->curr_ret_stack--;
+		*parent = old;
+	}
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */