tracing: infrastructure for supporting binary record

Impact: save on memory for tracing

Current tracers are typically using a struct(like struct ftrace_entry,
struct ctx_switch_entry, struct special_entr etc...)to record a binary
event. These structs can only record a their own kind of events.
A new kind of tracer need a new struct and a lot of code too handle it.

So we need a generic binary record for events. This infrastructure
is for this purpose.

[fweisbec@gmail.com: rebase against latest -tip, make it safe while sched
tracing as reported by Steven Rostedt]

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1236356510-8381-3-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 87 insertions, 0 deletions

diff --git a/kernel/trace/trace_bprintk.c b/kernel/trace/trace_bprintk.c
new file mode 100644
index 000000000000..1f8e532c3fb9
--- /dev/null
+++ b/kernel/trace/trace_bprintk.c
@@ -0,0 +1,87 @@
+/*
+ * trace binary printk
+ *
+ * Copyright (C) 2008 Lai Jiangshan <laijs@cn.fujitsu.com>
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/ftrace.h>
+#include <linux/string.h>
+#include <linux/ctype.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/fs.h>
+#include <linux/marker.h>
+#include <linux/uaccess.h>
+
+#include "trace.h"
+
+/* binary printk basic */
+static DEFINE_MUTEX(btrace_mutex);
+static int btrace_metadata_count;
+
+static inline void lock_btrace(void)
+{
+	mutex_lock(&btrace_mutex);
+}
+
+static inline void unlock_btrace(void)
+{
+	mutex_unlock(&btrace_mutex);
+}
+
+static void get_btrace_metadata(void)
+{
+	lock_btrace();
+	btrace_metadata_count++;
+	unlock_btrace();
+}
+
+static void put_btrace_metadata(void)
+{
+	lock_btrace();
+	btrace_metadata_count--;
+	unlock_btrace();
+}
+
+/* events tracer */
+int trace_bprintk_enable;
+
+static void start_bprintk_trace(struct trace_array *tr)
+{
+	get_btrace_metadata();
+	tracing_reset_online_cpus(tr);
+	trace_bprintk_enable = 1;
+}
+
+static void stop_bprintk_trace(struct trace_array *tr)
+{
+	trace_bprintk_enable = 0;
+	tracing_reset_online_cpus(tr);
+	put_btrace_metadata();
+}
+
+static int init_bprintk_trace(struct trace_array *tr)
+{
+	start_bprintk_trace(tr);
+	return 0;
+}
+
+static struct tracer bprintk_trace __read_mostly =
+{
+	.name	     = "events",
+	.init	     = init_bprintk_trace,
+	.reset	     = stop_bprintk_trace,
+	.start	     = start_bprintk_trace,
+	.stop	     = stop_bprintk_trace,
+};
+
+static __init int init_bprintk(void)
+{
+	return register_tracer(&bprintk_trace);
+}
+
+device_initcall(init_bprintk);