From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4C12EC04EB8 for ; Fri, 30 Nov 2018 15:23:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F064D2145D for ; Fri, 30 Nov 2018 15:23:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F064D2145D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726959AbeLACde (ORCPT ); Fri, 30 Nov 2018 21:33:34 -0500 Received: from mail.kernel.org ([198.145.29.99]:51692 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726624AbeLACde (ORCPT ); Fri, 30 Nov 2018 21:33:34 -0500 Received: from gandalf.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E997320868; Fri, 30 Nov 2018 15:23:52 +0000 (UTC) Date: Fri, 30 Nov 2018 10:23:51 -0500 From: Steven Rostedt To: Anders Roxell Cc: mingo@redhat.com, catalin.marinas@arm.com, will.deacon@arm.com, keescook@chromium.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Arnd Bergmann Subject: Re: [PATCH 3/3] arm64: ftrace: add cond_resched() to func ftrace_make_(call|nop) Message-ID: <20181130102351.61045b21@gandalf.local.home> In-Reply-To: <20181130150956.27620-1-anders.roxell@linaro.org> References: <20181130150956.27620-1-anders.roxell@linaro.org> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 30 Nov 2018 16:09:56 +0100 Anders Roxell wrote: > Both of those functions end up calling ftrace_modify_code(), which is > expensive because it changes the page tables and flush caches. > Microseconds add up because this is called in a loop for each dyn_ftrace > record, and this triggers the softlockup watchdog unless we let it sleep > occasionally. > Rework so that we call cond_resched() before going into the > ftrace_modify_code() function. > > Co-developed-by: Arnd Bergmann > Signed-off-by: Arnd Bergmann > Signed-off-by: Anders Roxell I'm fine with this patch, but I'm not placing an ack on this patch just because I don't know the repercussions of such a change. I'll let you folks take full responsibility ;-) -- Steve > --- > arch/arm64/kernel/ftrace.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > index de1a397d2d3f..9da38da58df7 100644 > --- a/arch/arm64/kernel/ftrace.c > +++ b/arch/arm64/kernel/ftrace.c > @@ -130,6 +130,11 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) > old = aarch64_insn_gen_nop(); > new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK); > > + /* This function can take a long time when sanitizers are enabled, so > + * lets make sure we allow RCU processing. > + */ > + cond_resched(); > + > return ftrace_modify_code(pc, old, new, true); > } > > @@ -188,6 +193,11 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, > > new = aarch64_insn_gen_nop(); > > + /* This function can take a long time when sanitizers are enabled, so > + * lets make sure we allow RCU processing. > + */ > + cond_resched(); > + > return ftrace_modify_code(pc, old, new, validate); > } >