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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 83153C64EB1 for ; Thu, 6 Dec 2018 16:06:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4E1EA20838 for ; Thu, 6 Dec 2018 16:06:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4E1EA20838 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com 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 S1726005AbeLFQG0 (ORCPT ); Thu, 6 Dec 2018 11:06:26 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:54406 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725862AbeLFQGZ (ORCPT ); Thu, 6 Dec 2018 11:06:25 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 11E7180D; Thu, 6 Dec 2018 08:06:25 -0800 (PST) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id D644E3F59C; Thu, 6 Dec 2018 08:06:24 -0800 (PST) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id F052C1AE0BD1; Thu, 6 Dec 2018 16:06:45 +0000 (GMT) Date: Thu, 6 Dec 2018 16:06:45 +0000 From: Will Deacon To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, catalin.marinas@arm.com, keescook@chromium.org, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, Anders Roxell , Ingo Molnar Subject: Re: [PATCH 2/2] arm64: ftrace: Set FTRACE_SCHEDULABLE before ftrace_modify_all_code() Message-ID: <20181206160645.GA4728@arm.com> References: <20181205174852.435233070@goodmis.org> <20181205183304.000714627@goodmis.org> <20181206132007.GB27744@arm.com> <20181206105914.7a29efa9@vmware.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181206105914.7a29efa9@vmware.local.home> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 06, 2018 at 10:59:14AM -0500, Steven Rostedt wrote: > On Thu, 6 Dec 2018 13:20:07 +0000 > Will Deacon wrote: > > > On Wed, Dec 05, 2018 at 12:48:54PM -0500, Steven Rostedt wrote: > > > From: "Steven Rostedt (VMware)" > > > > > > It has been reported that ftrace_replace_code() which is called by > > > ftrace_modify_all_code() can cause a soft lockup warning for an > > > allmodconfig kernel. This is because all the debug options enabled > > > causes the loop in ftrace_replace_code() (which loops over all the > > > functions being enabled where there can be 10s of thousands), is too > > > slow, and never schedules out. > > > > > > To solve this, setting FTRACE_SCHEDULABLE to the command passed into > > > ftrace_replace_code() will make it call cond_resched() in the loop, > > > which prevents the soft lockup warning from triggering. > > > > > > Link: http://lkml.kernel.org/r/20181204192903.8193-1-anders.roxell@linaro.org > > > > > > Reported-by: Anders Roxell > > > Signed-off-by: Steven Rostedt (VMware) > > > --- > > > arch/arm64/kernel/ftrace.c | 1 + > > > 1 file changed, 1 insertion(+) > > > > > > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > > > index 57e962290df3..9a8de0a79f97 100644 > > > --- a/arch/arm64/kernel/ftrace.c > > > +++ b/arch/arm64/kernel/ftrace.c > > > @@ -193,6 +193,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, > > > > > > void arch_ftrace_update_code(int command) > > > { > > > + command |= FTRACE_SCHEDULABLE; > > > ftrace_modify_all_code(command); > > > } > > > > Bikeshed: I'd probably go for FTRACE_MAY_SLEEP, but I'm not going to die > > on that hill so... > > I like bike sheds. Hmm, it's not too late to change this. Perhaps I > will. > > > > > Acked-by: Will Deacon > > Thanks! > > If I decide to change the name to MAY_SLEEP, I assume I can still keep > your Acked-by. Of course! Will