tracing: Encapsulate global_trace and remove dependencies on global vars

The global_trace variable in kernel/trace/trace.c has been kept 'static' and
local to that file so that it would not be used too much outside of that
file. This has paid off, even though there were lots of changes to make
the trace_array structure more generic (not depending on global_trace).

Removal of a lot of direct usages of global_trace is needed to be able to
create more trace_arrays such that we can add multiple buffers.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace.h

@@ -127,12 +127,21 @@ enum trace_flag_type {
 
 #define TRACE_BUF_SIZE		1024
 
+struct trace_array;
+
+struct trace_cpu {
+	struct trace_array	*tr;
+	struct dentry		*dir;
+	int			cpu;
+};
+
 /*
  * The CPU trace array - it consists of thousands of trace entries
  * plus some other descriptor data: (for example which task started
  * the trace, etc.)
  */
 struct trace_array_cpu {
+	struct trace_cpu	trace_cpu;
 	atomic_t		disabled;
 	void			*buffer_page;	/* ring buffer spare */
 
@@ -151,6 +160,8 @@ struct trace_array_cpu {
 	char			comm[TASK_COMM_LEN];
 };
 
+struct tracer;
+
 /*
  * The trace array - an array of per-CPU trace arrays. This is the
  * highest level data structure that individual tracers deal with.
@@ -161,9 +172,16 @@ struct trace_array {
 	struct list_head	list;
 	int			cpu;
 	int			buffer_disabled;
+	struct trace_cpu	trace_cpu;	/* place holder */
+	int			stop_count;
+	int			clock_id;
+	struct tracer		*current_trace;
 	unsigned int		flags;
 	cycle_t			time_start;
+	raw_spinlock_t		start_lock;
 	struct dentry		*dir;
+	struct dentry		*options;
+	struct dentry		*percpu_dir;
 	struct dentry		*event_dir;
 	struct list_head	systems;
 	struct list_head	events;
@@ -474,6 +492,7 @@ struct dentry *trace_create_file(const char *name,
 				 void *data,
 				 const struct file_operations *fops);
 
+struct dentry *tracing_init_dentry_tr(struct trace_array *tr);
 struct dentry *tracing_init_dentry(void);
 
 struct ring_buffer_event;
@@ -979,7 +998,7 @@ extern const char *__stop___trace_bprintk_fmt[];
 void trace_printk_init_buffers(void);
 void trace_printk_start_comm(void);
 int trace_keep_overwrite(struct tracer *tracer, u32 mask, int set);
-int set_tracer_flag(unsigned int mask, int enabled);
+int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled);
 
 #undef FTRACE_ENTRY
 #define FTRACE_ENTRY(call, struct_name, id, tstruct, print, filter)	\

kernel/trace/trace_irqsoff.c

@@ -561,8 +561,8 @@ static void __irqsoff_tracer_init(struct trace_array *tr)
 	save_flags = trace_flags;
 
 	/* non overwrite screws up the latency tracers */
-	set_tracer_flag(TRACE_ITER_OVERWRITE, 1);
-	set_tracer_flag(TRACE_ITER_LATENCY_FMT, 1);
+	set_tracer_flag(tr, TRACE_ITER_OVERWRITE, 1);
+	set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, 1);
 
 	tracing_max_latency = 0;
 	irqsoff_trace = tr;
@@ -581,8 +581,8 @@ static void irqsoff_tracer_reset(struct trace_array *tr)
 
 	stop_irqsoff_tracer(tr, is_graph());
 
-	set_tracer_flag(TRACE_ITER_LATENCY_FMT, lat_flag);
-	set_tracer_flag(TRACE_ITER_OVERWRITE, overwrite_flag);
+	set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, lat_flag);
+	set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag);
 }
 
 static void irqsoff_tracer_start(struct trace_array *tr)

kernel/trace/trace_sched_wakeup.c

@@ -543,8 +543,8 @@ static int __wakeup_tracer_init(struct trace_array *tr)
 	save_flags = trace_flags;
 
 	/* non overwrite screws up the latency tracers */
-	set_tracer_flag(TRACE_ITER_OVERWRITE, 1);
-	set_tracer_flag(TRACE_ITER_LATENCY_FMT, 1);
+	set_tracer_flag(tr, TRACE_ITER_OVERWRITE, 1);
+	set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, 1);
 
 	tracing_max_latency = 0;
 	wakeup_trace = tr;
@@ -573,8 +573,8 @@ static void wakeup_tracer_reset(struct trace_array *tr)
 	/* make sure we put back any tasks we are tracing */
 	wakeup_reset(tr);
 
-	set_tracer_flag(TRACE_ITER_LATENCY_FMT, lat_flag);
-	set_tracer_flag(TRACE_ITER_OVERWRITE, overwrite_flag);
+	set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, lat_flag);
+	set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag);
 }
 
 static void wakeup_tracer_start(struct trace_array *tr)