[PATCH 2/2] tracing: Disable events in reverse order of their enable operation

[Petr Pavlu]

Make the disable operation in __ftrace_event_enable_disable() use the
reverse order of the respective enable operation.

This has two minor benefits:
* Disabling of buffered events via trace_buffered_event_disable() is
  done after unregistering the trace event. It closes a small window
  where an event would be still registered and could be hit, but would
  unnecessarily go directly to a ring buffer.
* The SOFT_DISABLED flag is now consistently set only when SOFT_MODE is
  also set.

Signed-off-by: Petr Pavlu <petr.pa...@suse.com>
---
 kernel/trace/trace_events.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index f29e815ca5b2..5f14d68a0ced 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -633,9 +633,6 @@ static int __ftrace_event_enable_disable(struct 
trace_event_file *file,
                        if (atomic_dec_return(&file->sm_ref) > 0)
                                break;
                        disable = file->flags & EVENT_FILE_FL_SOFT_DISABLED;
-                       clear_bit(EVENT_FILE_FL_SOFT_MODE_BIT, &file->flags);
-                       /* Disable use of trace_buffered_event */
-                       trace_buffered_event_disable();
                } else
                        disable = !(file->flags & EVENT_FILE_FL_SOFT_MODE);
 
@@ -653,11 +650,17 @@ static int __ftrace_event_enable_disable(struct 
trace_event_file *file,
 
                        call->class->reg(call, TRACE_REG_UNREGISTER, file);
                }
-               /* If in SOFT_MODE, just set the SOFT_DISABLE_BIT, else clear 
it */
-               if (file->flags & EVENT_FILE_FL_SOFT_MODE)
-                       set_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags);
-               else
+
+               if (soft_disable) {
+                       /* Complete going out of SOFT_MODE */
                        clear_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, 
&file->flags);
+                       clear_bit(EVENT_FILE_FL_SOFT_MODE_BIT, &file->flags);
+                       /* Disable use of trace_buffered_event */
+                       trace_buffered_event_disable();
+               } else if (file->flags & EVENT_FILE_FL_SOFT_MODE) {
+                       /* If in SOFT_MODE, just set the SOFT_DISABLE_BIT */
+                       set_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags);
+               }
                break;
        case 1:
                /*
-- 
2.35.3