Merge tag 'trace-3.8-rc3-regression-fix' of git://git.kernel.org/pub/scm/linux/kernel...

Pull tracing regression fixes from Steven Rostedt:
 "The clean up patch commit 0fb9656d957d "tracing: Make tracing_enabled
  be equal to tracing_on" caused two regressions.

   1) The irqs off latency tracer no longer starts if tracing_on is off
      when the tracer is set, and then tracing_on is enabled.  The
      tracing_on file needs the hook that tracing_enabled had to enable
      tracers if they request it (call the tracer's start() method).

   2) That commit had a separate change that really should have been a
      separate patch, but it must have been added accidently with the -a
      option of git commit.  But as the change is still related to the
      commit it wasn't noticed in review.  That change, changed the way
      blocking is done by the trace_pipe file with respect to the
      tracing_on settings.  I've been told that this change breaks
      current userspace, and this specific change is being reverted."

* tag 'trace-3.8-rc3-regression-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Fix regression of trace_pipe
  tracing: Fix regression with irqsoff tracer and tracing_on file

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 1bbfa0446507405d2fce92036322224170d7411e..3c13e46d7d24e1ecbdeb532f6538354f6eca7ddf 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3454,7 +3454,7 @@ static int tracing_wait_pipe(struct file *filp)
                        return -EINTR;
 
                /*
-                * We block until we read something and tracing is enabled.
+                * We block until we read something and tracing is disabled.
                 * We still block if tracing is disabled, but we have never
                 * read anything. This allows a user to cat this file, and
                 * then enable tracing. But after we have read something,
@@ -3462,7 +3462,7 @@ static int tracing_wait_pipe(struct file *filp)
                 *
                 * iter->pos will be 0 if we haven't read anything.
                 */
-               if (tracing_is_enabled() && iter->pos)
+               if (!tracing_is_enabled() && iter->pos)
                        break;
        }
 
@@ -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)++;