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Date:   Tue, 8 Sep 2020 11:55:27 +0900
From:   Masami Hiramatsu <mhiramat@kernel.org>
To:     fche@redhat.com (Frank Ch. Eigler)
Cc:     peterz@infradead.org, Ingo Molnar <mingo@kernel.org>,
        linux-kernel@vger.kernel.org, Eddy_Wu@trendmicro.com,
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        linux-arch@vger.kernel.org, cameron@moodycamel.com,
        oleg@redhat.com, will@kernel.org, paulmck@kernel.org,
        systemtap@sourceware.org
Subject: Re: [PATCH v5 00/21] kprobes: Unify kretprobe trampoline handlers
 and make kretprobe lockless
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On Mon, 07 Sep 2020 13:44:19 -0400
fche@redhat.com (Frank Ch. Eigler) wrote:

> Masami Hiramatsu <mhiramat@kernel.org> writes:
> 
> > Sorry, for noticing this point, I Cc'd to systemtap. Is systemtap taking
> > care of spinlock too?
> 
> On PRREMPT_RT configurations, systemtap uses the raw_spinlock_t
> types/functions, to keep its probe handlers as atomic as we can make them.

OK, if the lock is only used in the probe handlers, there should be
no problem. Even if a probe hits in the NMI which happens in another
kprobe handler, the probe does not call its handler (because we don't
support nested kprobes* yet).
But maybe you'll get warnings if you enable the lockdep.

* https://lkml.kernel.org/r/158894789510.14896.13461271606820304664.stgit@devnote2
It seems that we need more work for the nested kprobes.

Thank you,

-- 
Masami Hiramatsu <mhiramat@kernel.org>