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The clean up patch commit 0fb9656d "tracing: Make tracing_enabled be equal

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

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
This commit is contained in:
Linus Torvalds 2013-01-14 20:22:16 -08:00
commit 406089d015
1 changed files with 11 additions and 4 deletions
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15
kernel/trace/trace.c
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@ -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)++;