[PATCH] lib/spinlock_debug: Prevent unnecessary recursive spin_dump()

[Byungchul Park]

For your information, there is another patch I posted which looks similar
to this patch, but is totally different, that is,
https://lkml.org/lkml/2016/3/11/192, trying to solve a deadlock problem.

In that patch, I tried to make printk async to avoid the deadlock but I
found Sergey and Jan were already working on the asynchronous printk().
That is, https://lkml.org/lkml/2016/3/23/316. Thus I decided to wait the
work to be done and to work on my patch again based on the patch by Sergey
and Jan.

On the other hand, this patch is not for avoiding the deadlock, but for
avoiding unnecessary recursion. See the backtrace shown below.

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