Commit cf6ab6d9 authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
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tracing: Add ref count to tracer for when they are being read by pipe 



When one of the trace pipe files are being read (by either the trace_pipe
or trace_pipe_raw), do not allow the current_trace to change. By adding
a ref count that is incremented when the pipe files are opened, will
prevent the current_trace from being changed.

This will allow for the removal of the global trace_types_lock from
reading the pipe buffers (which is currently a bottle neck).

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 97bf6af1

kernel/trace/trace.c

+15 −1
Original line number Diff line number Diff line
@@ -4140,6 +4140,12 @@ static int tracing_set_tracer(struct trace_array *tr, const char *buf) 
		goto out;

	}



	/* If trace pipe files are being read, we can't change the tracer */

	if (tr->current_trace->ref) {

		ret = -EBUSY;

		goto out;

	}



	trace_branch_disable();



	tr->current_trace->enabled--;
@@ -4363,6 +4369,8 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp) 
		iter->trace->pipe_open(iter);



	nonseekable_open(inode, filp);



	tr->current_trace->ref++;

out:

	mutex_unlock(&trace_types_lock);

	return ret;
@@ -4382,6 +4390,8 @@ static int tracing_release_pipe(struct inode *inode, struct file *file) 


	mutex_lock(&trace_types_lock);



	tr->current_trace->ref--;



	if (iter->trace->pipe_close)

		iter->trace->pipe_close(iter);
@@ -5331,6 +5341,8 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp) 


	filp->private_data = info;



	tr->current_trace->ref++;



	mutex_unlock(&trace_types_lock);



	ret = nonseekable_open(inode, filp);
@@ -5437,6 +5449,8 @@ static int tracing_buffers_release(struct inode *inode, struct file *file) 


	mutex_lock(&trace_types_lock);



	iter->tr->current_trace->ref--;



	__trace_array_put(iter->tr);



	if (info->spare)
@@ -6416,7 +6430,7 @@ static int instance_delete(const char *name) 
		goto out_unlock;



	ret = -EBUSY;

	if (tr->ref)

	if (tr->ref || (tr->current_trace && tr->current_trace->ref))

		goto out_unlock;



	list_del(&tr->list);

kernel/trace/trace.h

+1 −0
Original line number Diff line number Diff line
@@ -388,6 +388,7 @@ struct tracer { 
	struct tracer		*next;

	struct tracer_flags	*flags;

	int			enabled;

	int			ref;

	bool			print_max;

	bool			allow_instances;

#ifdef CONFIG_TRACER_MAX_TRACE

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