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Date:   Tue, 12 Oct 2021 22:30:39 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     =?UTF-8?B?546L6LSH?= <yun.wang@linux.alibaba.com>
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Subject: Re: [PATCH 1/2] ftrace: disable preemption on the testing of
 recursion
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On Wed, 13 Oct 2021 10:04:52 +0800
王贇 <yun.wang@linux.alibaba.com> wrote:

> I see, while the user can still check smp_processor_id() after trylock
> return bit 0...

But preemption would have already been disabled. That's because a bit 0
means that a recursion check has already been made by a previous
caller and this one is nested, thus preemption is already disabled.
If bit is 0, then preemption had better be disabled as well.

-- Steve