Re: [PATCH] arm64: ftrace: stop using kstop_machine to enable/disable tracing

[Steven Rostedt <rostedt@goodmis.org>]

On Sat, 28 Nov 2015 15:50:09 +0800
Li Bin <huawei.libin@huawei.com> wrote:

> On arm64, kstop_machine which is hugely disruptive to a running
> system is not needed to convert nops to ftrace calls or back,
> because that modifed code is a single 32bit instructions which
> is impossible to cross cache (or page) boundaries, and the used str
> instruction is single-copy atomic.

Is this really true? I thought that arm (and then perhaps arm64) has
some 2 byte instructions. If that's the case it is very well possible
that a 4 byte instruction can cross cache lines.

-- Steve

> 
> Cc: <stable@vger.kernel.org> # 3.18+
> Signed-off-by: Li Bin <huawei.libin@huawei.com>
> ---
>  arch/arm64/kernel/ftrace.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)