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tracing: trace_remove_event_call() should fail if call/file is in use

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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>
This commit is contained in:
Oleg Nesterov 2013-07-29 19:50:33 +02:00 • committed by Steven Rostedt
parent 776164c1fa
commit 2816c551c7
2 changed files with 35 additions and 4 deletions
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2
include/linux/ftrace_event.h
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@ -332,7 +332,7 @@ extern int trace_define_field(struct ftrace_event_call *call, const char *type,
const char *name, int offset, int size,
int is_signed, int filter_type);
extern int trace_add_event_call(struct ftrace_event_call *call);
extern void trace_remove_event_call(struct ftrace_event_call *call);
extern int trace_remove_event_call(struct ftrace_event_call *call);
#define is_signed_type(type) (((type)(-1)) < (type)1)