tracing: Add interface to allow multiple trace buffers
Add the interface ("instances" directory) to add multiple buffers
to ftrace. To create a new instance, simply do a mkdir in the
instances directory:
This will create a directory with the following:
# cd instances
# mkdir foo
# ls foo
buffer_size_kb free_buffer trace_clock trace_pipe
buffer_total_size_kb set_event trace_marker tracing_enabled
events/ trace trace_options tracing_on
Currently only events are able to be set, and there isn't a way
to delete a buffer when one is created (yet).
Note, the i_mutex lock is dropped from the parent "instances"
directory during the mkdir operation. As the "instances" directory
can not be renamed or deleted (created on boot), I do not see
any harm in dropping the lock. The creation of the sub directories
is protected by trace_types_lock mutex, which only lets one
instance get into the code path at a time. If two tasks try to
create or delete directories of the same name, only one will occur
and the other will fail with -EEXIST.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 68cad7a..883fe0b 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -175,6 +175,7 @@
struct trace_array {
struct ring_buffer *buffer;
struct list_head list;
+ char *name;
int cpu;
int buffer_disabled;
struct trace_cpu trace_cpu; /* place holder */
@@ -999,6 +1000,7 @@
}
extern void trace_event_enable_cmd_record(bool enable);
+extern int event_trace_add_tracer(struct dentry *parent, struct trace_array *tr);
extern struct mutex event_mutex;
extern struct list_head ftrace_events;