On Mon, 7 Nov 2016 15:14:20 -0800
Alexei Starovoitov <a...@fb.com> wrote:
> ftrace_shutdown() checks for sanity of ftrace records
> and if dyn_ftrace->flags is not zero, it will warn.
> It can happen that 'flags' are set to FTRACE_FL_DISABLED at this point,
> since some module was loaded, but before ftrace_module_enable()
> cleared the flags for this module.
>
> In other words the module.c is doing:
> ftrace_module_init(mod); // calls ftrace_update_code() that sets
> flags=FTRACE_FL_DISABLED
> ... // here ftrace_shutdown() is called that warns, since
> err = prepare_coming_module(mod); // didn't have a chance to clear
> FTRACE_FL_DISABLED
>
> Fix it by ignoring disabled records.
> It's similar to what __ftrace_hash_rec_update() is already doing.
>
Alexei,
Do you have a clear reproducer of this bug?
-- Steve
> Signed-off-by: Alexei Starovoitov <a...@kernel.org>
> ---
> kernel/trace/ftrace.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 2050a7652a86..326498baab83 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -2763,7 +2763,7 @@ static int ftrace_shutdown(struct ftrace_ops *ops, int
> command)
> struct dyn_ftrace *rec;
>
> do_for_each_ftrace_rec(pg, rec) {
> - if (FTRACE_WARN_ON_ONCE(rec->flags))
> + if (FTRACE_WARN_ON_ONCE(rec->flags &
> ~FTRACE_FL_DISABLED))
> pr_warn(" %pS flags:%lx\n",
> (void *)rec->ip, rec->flags);
> } while_for_each_ftrace_rec();
