From: Masami Hiramatsu <mhiramat@kernel.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: peterz@infradead.org, Ingo Molnar <mingo@kernel.org>,
linux-kernel@vger.kernel.org, Eddy_Wu@trendmicro.com,
x86@kernel.org, davem@davemloft.net, rostedt@goodmis.org,
naveen.n.rao@linux.ibm.com, anil.s.keshavamurthy@intel.com,
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
Date: Thu, 3 Sep 2020 11:02:26 +0900 [thread overview]
Message-ID: <20200903110226.8963179e6a7c978e2d56c595@kernel.org> (raw)
In-Reply-To: <20200903103954.68f0c97da57b3679169ce3a7@kernel.org>
On Thu, 3 Sep 2020 10:39:54 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:
> OK, I've confirmed that the lockdep warns on kretprobe from INT3
> with your fix. Of course make it lockless then warning is gone.
> But even without the lockless patch, this warning can be false-positive
> because we prohibit nested kprobe call, right?
>
> If the kprobe user handler uses a spinlock, the spinlock is used
> only in that handler (and in the context between kprobe_busy_begin/end),
> it will be safe since the spinlock is not nested.
> But if the spinlock is shared with other context, it will be dangerous
> because it can be interrupted by NMI (including INT3). This also applied
> to the function which is called from kprobe user handlers, thus user
> has to take care of it.
Sorry, for noticing this point, I Cc'd to systemtap. Is systemtap taking
care of spinlock too?
Thank you,
--
Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2020-09-03 2:02 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <159870598914.1229682.15230803449082078353.stgit@devnote2>
[not found] ` <20200901190808.GK29142@worktop.programming.kicks-ass.net>
[not found] ` <20200902093739.8bd13603380951eaddbcd8a5@kernel.org>
[not found] ` <20200902070226.GG2674@hirez.programming.kicks-ass.net>
[not found] ` <20200902171755.b126672093a3c5d1b3a62a4f@kernel.org>
[not found] ` <20200902093613.GY1362448@hirez.programming.kicks-ass.net>
[not found] ` <20200902221926.f5cae5b4ad00b8d8f9ad99c7@kernel.org>
[not found] ` <20200902134252.GH1362448@hirez.programming.kicks-ass.net>
2020-09-03 1:39 ` Masami Hiramatsu
2020-09-03 2:02 ` Masami Hiramatsu [this message]
2020-09-07 17:44 ` Frank Ch. Eigler
2020-09-08 2:55 ` Masami Hiramatsu
2020-09-08 10:37 ` peterz
2020-09-08 11:15 ` Eddy_Wu
2020-09-08 11:33 ` peterz
2020-09-08 15:09 ` Masami Hiramatsu
2020-09-09 5:28 ` Masami Hiramatsu
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