From 2df8f8a6a897ebf4c5613b5be6103d33b2a21520 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 11 Jan 2013 16:14:10 -0500 Subject: [PATCH] tracing: Fix regression with irqsoff tracer and tracing_on file Commit 02404baf1b47 "tracing: Remove deprecated tracing_enabled file" removed the tracing_enabled file as it never worked properly and the tracing_on file should be used instead. But the tracing_on file didn't call into the tracers start/stop routines like the tracing_enabled file did. This caused trace-cmd to break when it enabled the irqsoff tracer. If you just did "echo irqsoff > current_tracer" then it would work properly. But the tool trace-cmd disables tracing first by writing "0" into the tracing_on file. Then it writes "irqsoff" into current_tracer and then writes "1" into tracing_on. Unfortunately, the above commit changed the irqsoff tracer to check the tracing_on status instead of the tracing_enabled status. If it's disabled then it does not start the tracer internals. The problem is that writing "1" into tracing_on does not call the tracers "start" routine like writing "1" into tracing_enabled did. This makes the irqsoff tracer not start when using the trace-cmd tool, and is a regression for userspace. Simple fix is to have the tracing_on file call the tracers start() method when being enabled (and the stop() method when disabled). Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 1bbfa044650..f3ec1cfb0de 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4817,10 +4817,17 @@ rb_simple_write(struct file *filp, const char __user *ubuf, return ret; if (buffer) { - if (val) + mutex_lock(&trace_types_lock); + if (val) { ring_buffer_record_on(buffer); - else + if (current_trace->start) + current_trace->start(tr); + } else { ring_buffer_record_off(buffer); + if (current_trace->stop) + current_trace->stop(tr); + } + mutex_unlock(&trace_types_lock); } (*ppos)++;