Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752288AbbK1P6a (ORCPT ); Sat, 28 Nov 2015 10:58:30 -0500 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.230]:10010 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752097AbbK1P62 (ORCPT ); Sat, 28 Nov 2015 10:58:28 -0500 Date: Sat, 28 Nov 2015 10:58:19 -0500 From: Steven Rostedt To: Li Bin Cc: , , , , , , Subject: Re: [PATCH] arm64: ftrace: stop using kstop_machine to enable/disable tracing Message-ID: <20151128105819.3451ab3e@grimm.local.home> In-Reply-To: <1448697009-17211-1-git-send-email-huawei.libin@huawei.com> References: <1448697009-17211-1-git-send-email-huawei.libin@huawei.com> X-Mailer: Claws Mail 3.13.0 (GTK+ 2.24.28; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.130:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1016 Lines: 26 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(-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/