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tracing: Fix regression with tracing_on

The change to make tracing_on affect only the ftrace ring buffer, caused
a bug where it wont affect any ring buffer. The problem was that the buffer
of the trace_array was passed to the write function and not the trace array
itself.

The trace_array can change the buffer when running a latency tracer. If this
happens, then the buffer being disabled may not be the buffer currently used
by ftrace. This will cause the tracing_on file to become useless.

The simple fix is to pass the trace_array to the write function instead of
the buffer. Then the actual buffer may be changed.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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1 parent 6e48b55 commit 348f0fc238efb441a28e7644c51f9fd3001b228a Steven Rostedt committed with rostedt Apr 16, 2012
Showing with 5 additions and 3 deletions.
  1. +5 −3 kernel/trace/trace.c
@@ -4629,7 +4629,8 @@ static ssize_t
rb_simple_read(struct file *filp, char __user *ubuf,
size_t cnt, loff_t *ppos)
{
- struct ring_buffer *buffer = filp->private_data;
+ struct trace_array *tr = filp->private_data;
+ struct ring_buffer *buffer = tr->buffer;
char buf[64];
int r;
@@ -4647,7 +4648,8 @@ static ssize_t
rb_simple_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
{
- struct ring_buffer *buffer = filp->private_data;
+ struct trace_array *tr = filp->private_data;
+ struct ring_buffer *buffer = tr->buffer;
unsigned long val;
int ret;
@@ -4734,7 +4736,7 @@ static __init int tracer_init_debugfs(void)
&trace_clock_fops);
trace_create_file("tracing_on", 0644, d_tracer,
- global_trace.buffer, &rb_simple_fops);
+ &global_trace, &rb_simple_fops);
#ifdef CONFIG_DYNAMIC_FTRACE
trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,

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