tracing: trace_remove_event_call() should fail if call/file is in use
authorOleg Nesterov <oleg@redhat.com>
Mon, 29 Jul 2013 17:50:33 +0000 (19:50 +0200)
committerSteven Rostedt <rostedt@goodmis.org>
Wed, 31 Jul 2013 17:12:48 +0000 (13:12 -0400)
commit2816c551c796ec14620325b2c9ed75b9979d3125
treec4bc262514de5ef265001411bcdf7ad65916eae9
parent776164c1faac4966ab14418bb0922e1820da1d19
tracing: trace_remove_event_call() should fail if call/file is in use

Change trace_remove_event_call(call) to return the error if this
call is active. This is what the callers assume but can't verify
outside of the tracing locks. Both trace_kprobe.c/trace_uprobe.c
need the additional changes, unregister_trace_probe() should abort
if trace_remove_event_call() fails.

The caller is going to free this call/file so we must ensure that
nobody can use them after trace_remove_event_call() succeeds.
debugfs should be fine after the previous changes and event_remove()
does TRACE_REG_UNREGISTER, but still there are 2 reasons why we need
the additional checks:

- There could be a perf_event(s) attached to this tp_event, so the
  patch checks ->perf_refcount.

- TRACE_REG_UNREGISTER can be suppressed by FTRACE_EVENT_FL_SOFT_MODE,
  so we simply check FTRACE_EVENT_FL_ENABLED protected by event_mutex.

Link: http://lkml.kernel.org/r/20130729175033.GB26284@redhat.com
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
include/linux/ftrace_event.h
kernel/trace/trace_events.c