linux-kernel - Re: [PATCH 4/9] ftrace: Add enable/disable ftrace

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Date:	Mon, 28 Nov 2011 21:02:32 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Jiri Olsa <jolsa@...hat.com>, fweisbec@...il.com, mingo@...hat.com,
	paulus@...ba.org, acme@...stprotocols.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/9] ftrace: Add enable/disable ftrace_ops control
 interface

On Mon, 2011-11-28 at 14:26 -0500, Steven Rostedt wrote:
> 
> Are jump labels safe in NMI context yet? If not, this will need to wait
> till we make it so. 

I don't think they are, we currently very much rely on that
stop_machine() crap. NMIs can go straight through that.

I think you can make it work with the stop_machine()-less approach,
because then the NMI will trap on the INT3 which will wait for
completion, sync and resume the NMI.

That of course relies on the NMI vs IRET crap getting sorted.

But even then, that's highly arch specific and I'm not sure we can make
all archs that support both jump_label and NMIs work.

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