Merge tag 'trace-fixes-3.13-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fix from Steven Rostedt:
 "A regression showed up that there's a large delay when enabling all
  events.  This was prevalent when FTRACE_SELFTEST was enabled which
  enables all events several times, and caused the system bootup to
  pause for over a minute.

  This was tracked down to an addition of a synchronize_sched()
  performed when system call tracepoints are unregistered.

  The synchronize_sched() is needed between the unregistering of the
  system call tracepoint and a deletion of a tracing instance buffer.
  But placing the synchronize_sched() in the unreg of *every* system
  call tracepoint is a bit overboard.  A single synchronize_sched()
  before the deletion of the instance is sufficient"

* tag 'trace-fixes-3.13-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Only run synchronize_sched() at instance deletion time

2 files changed, 3 insertions, 10 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index f919a2e21bf3..a11800ae96de 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2314,6 +2314,9 @@ int event_trace_del_tracer(struct trace_array *tr)
         /* Disable any running events */
         __ftrace_set_clr_event_nolock(tr, NULL, NULL, NULL, 0);
 
+        /* Access to events are within rcu_read_lock_sched() */
+        synchronize_sched();
+
         down_write(&trace_event_sem);
         __trace_remove_event_dirs(tr);
         debugfs_remove_recursive(tr->event_dir);
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index e4b6d11bdf78..ea90eb5f6f17 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -431,11 +431,6 @@ static void unreg_event_syscall_enter(struct ftrace_event_file *file,
         if (!tr->sys_refcount_enter)
                 unregister_trace_sys_enter(ftrace_syscall_enter, tr);
         mutex_unlock(&syscall_trace_lock);
-        /*
-         * Callers expect the event to be completely disabled on
-         * return, so wait for current handlers to finish.
-         */
-        synchronize_sched();
 }
 
 static int reg_event_syscall_exit(struct ftrace_event_file *file,
@@ -474,11 +469,6 @@ static void unreg_event_syscall_exit(struct ftrace_event_file *file,
         if (!tr->sys_refcount_exit)
                 unregister_trace_sys_exit(ftrace_syscall_exit, tr);
         mutex_unlock(&syscall_trace_lock);
-        /*
-         * Callers expect the event to be completely disabled on
-         * return, so wait for current handlers to finish.
-         */
-        synchronize_sched();
 }
 
 static int __init init_syscall_trace(struct ftrace_event_call *call)