From mboxrd@z Thu Jan 1 00:00:00 1970 From: rostedt@goodmis.org (Steven Rostedt) Date: Sat, 28 Nov 2015 10:58:19 -0500 Subject: [PATCH] arm64: ftrace: stop using kstop_machine to enable/disable tracing In-Reply-To: <1448697009-17211-1-git-send-email-huawei.libin@huawei.com> References: <1448697009-17211-1-git-send-email-huawei.libin@huawei.com> Message-ID: <20151128105819.3451ab3e@grimm.local.home> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Sat, 28 Nov 2015 15:50:09 +0800 Li Bin 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: # 3.18+ > Signed-off-by: Li Bin > --- > arch/arm64/kernel/ftrace.c | 5 +++++ > 1 files changed, 5 insertions(+), 0 deletions(-)