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authorSteven Noonan <steven@uplinklabs.net>2008-09-19 03:06:43 -0700
committerIngo Molnar <mingo@elte.hu>2008-10-14 10:37:43 +0200
commitfb1b6d8b5154c692172a424e45fbd0573295cb93 (patch)
treed9a7ad2c629a6133998402354e77cd721e4962b4 /kernel/trace/trace_nop.c
parent5bf9a1ee350a10feb94107de32a203d81fbbe706 (diff)
downloadlinux-fb1b6d8b5154c692172a424e45fbd0573295cb93.tar.gz
ftrace: add nop tracer
A no-op tracer which can serve two purposes: 1. A template for development of a new tracer. 2. A convenient way to see ftrace_printk() calls without an irrelevant trace making the output messy. [ mingo@elte.hu: resolved conflicts ] Signed-off-by: Steven Noonan <steven@uplinklabs.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/trace/trace_nop.c')
-rw-r--r--kernel/trace/trace_nop.c65
1 files changed, 65 insertions, 0 deletions
diff --git a/kernel/trace/trace_nop.c b/kernel/trace/trace_nop.c
new file mode 100644
index 000000000000..dafaefb84038
--- /dev/null
+++ b/kernel/trace/trace_nop.c
@@ -0,0 +1,65 @@
+/*
+ * nop tracer
+ *
+ * Copyright (C) 2008 Steven Noonan <steven@uplinklabs.net>
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/ftrace.h>
+
+#include "trace.h"
+
+static struct trace_array *ctx_trace;
+
+static void start_nop_trace(struct trace_array *tr)
+{
+ /* Nothing to do! */
+}
+
+static void stop_nop_trace(struct trace_array *tr)
+{
+ /* Nothing to do! */
+}
+
+static void nop_trace_init(struct trace_array *tr)
+{
+ ctx_trace = tr;
+
+ if (tr->ctrl)
+ start_nop_trace(tr);
+}
+
+static void nop_trace_reset(struct trace_array *tr)
+{
+ if (tr->ctrl)
+ stop_nop_trace(tr);
+}
+
+static void nop_trace_ctrl_update(struct trace_array *tr)
+{
+ /* When starting a new trace, reset the buffers */
+ if (tr->ctrl)
+ start_nop_trace(tr);
+ else
+ stop_nop_trace(tr);
+}
+
+static struct tracer nop_trace __read_mostly =
+{
+ .name = "nop",
+ .init = nop_trace_init,
+ .reset = nop_trace_reset,
+ .ctrl_update = nop_trace_ctrl_update,
+#ifdef CONFIG_FTRACE_SELFTEST
+ .selftest = trace_selftest_startup_nop,
+#endif
+};
+
+__init static int init_nop_trace(void)
+{
+ return register_tracer(&nop_trace);
+}
+device_initcall(init_nop_trace);