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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C8AECCA485 for ; Thu, 9 Jun 2022 13:06:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343701AbiFINGj (ORCPT ); Thu, 9 Jun 2022 09:06:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54586 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236268AbiFINGc (ORCPT ); Thu, 9 Jun 2022 09:06:32 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 724408215A; Thu, 9 Jun 2022 06:06:30 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id EE7B921F31; Thu, 9 Jun 2022 13:06:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1654779989; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=fQ7/fX+AXX7RSe4KqEkRum0uc4vC19BTUP6nq2wTOec=; b=o28ZaXYpRsbDNeH7DdY3dJH3Fnc3dlxZT8L+x/2aFmo5tE4BAEDzQGW4+i3DDhNGrDHekt G23+f/oOyTepRO03yIh1gixSASehX2C07pg1fm0i3R3KDgn22PhYw8V9jvCq8nE2YIN+/O p3FQSqV1HR0kVCZZzDry3RvUltYRjYI= Received: from suse.cz (unknown [10.100.208.146]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id CEE382C141; Thu, 9 Jun 2022 13:06:27 +0000 (UTC) Date: Thu, 9 Jun 2022 15:06:00 +0200 From: Petr Mladek To: Peter Zijlstra Cc: ink@jurassic.park.msu.ru, mattst88@gmail.com, vgupta@kernel.org, linux@armlinux.org.uk, ulli.kroll@googlemail.com, linus.walleij@linaro.org, shawnguo@kernel.org, Sascha Hauer , kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, tony@atomide.com, khilman@kernel.org, catalin.marinas@arm.com, will@kernel.org, guoren@kernel.org, bcain@quicinc.com, chenhuacai@kernel.org, kernel@xen0n.name, geert@linux-m68k.org, sammy@sammy.net, monstr@monstr.eu, tsbogend@alpha.franken.de, dinguyen@kernel.org, jonas@southpole.se, stefan.kristiansson@saunalahti.fi, shorne@gmail.com, James.Bottomley@hansenpartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, richard@nod.at, anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, acme@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, namhyung@kernel.org, jgross@suse.com, srivatsa@csail.mit.edu, amakhalov@vmware.com, pv-drivers@vmware.com, boris.ostrovsky@oracle.com, chris@zankel.net, jcmvbkbc@gmail.com, rafael@kernel.org, lenb@kernel.org, pavel@ucw.cz, gregkh@linuxfoundation.org, mturquette@baylibre.com, sboyd@kernel.org, daniel.lezcano@linaro.org, lpieralisi@kernel.org, sudeep.holla@arm.com, agross@kernel.org, bjorn.andersson@linaro.org, anup@brainfault.org, thierry.reding@gmail.com, jonathanh@nvidia.com, jacob.jun.pan@linux.intel.com, Arnd Bergmann , yury.norov@gmail.com, andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk, rostedt@goodmis.org, senozhatsky@chromium.org, john.ogness@linutronix.de, paulmck@kernel.org, frederic@kernel.org, quic_neeraju@quicinc.com, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, jpoimboe@kernel.org, linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-perf-users@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, linux-xtensa@linux-xtensa.org, linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, linux-clk@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-arch@vger.kernel.org, rcu@vger.kernel.org Subject: Re: [PATCH 24/36] printk: Remove trace_.*_rcuidle() usage Message-ID: References: <20220608142723.103523089@infradead.org> <20220608144517.444659212@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org On Thu 2022-06-09 12:02:04, Peter Zijlstra wrote: > On Thu, Jun 09, 2022 at 11:16:46AM +0200, Petr Mladek wrote: > > On Wed 2022-06-08 16:27:47, Peter Zijlstra wrote: > > > The problem, per commit fc98c3c8c9dc ("printk: use rcuidle console > > > tracepoint"), was printk usage from the cpuidle path where RCU was > > > already disabled. > > > > > Does this "prevent" calling printk() a safe way in code with > > RCU disabled? > > On x86_64, yes. Other architectures, less so. > > Specifically, the objtool noinstr validation pass will warn at build > time (DEBUG_ENTRY=y) if any noinstr/cpuidle code does a call to > non-vetted code like printk(). > > At the same time; there's a few hacks that allow WARN to work, but > mostly if you hit WARN in entry/noinstr you get to keep the pieces in > any case. > > On other architecture we'll need to rely on runtime coverage with > PROVE_RCU. That is, if a splat like in the above mentioned commit > happens again, we'll need to fix it by adjusting the callchain, not by > mucking about with RCU state. Makes sense. Feel free to use for this patch: Acked-by: Petr Mladek > > Therefore if this patch allows to remove some tricky tracing > > code then it might be worth it. But if trace_console_rcuidle() > > variant is still going to be available then I would keep using it. > > My ultimate goal is to delete trace_.*_rcuidle() and RCU_NONIDLE() > entirely. We're close, but not quite there yet. I keep my fingers crossed. Best Regards, Petr 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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CAFCDCCA481 for ; Thu, 9 Jun 2022 13:06:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=W6YTSxu5bi4uvUKktTKZFzDlbMm2k7IRiA81XUdpMes=; b=4PBsi3qPtpS2FB Xb6GuW9eIVL4JyCpy14WMjZg+G6G14JNaZNWfVsJx+aCOVaPCRBcx8unHVN0MbqtQVy/+Eje6ArX1 l/FpESRy86+i38xNXpA9qGuff1AVyUAhCX/2o2WpUZ6VsMdrnPcD2WyTT/VP5RWRVpXjiaeYyPrCb 3xyWrcViMK+RM5SSSiuyyAzoVtrOPpIXzmM6eyQjJ72dgnAL6mBakxxz2RfNR218O7uPWd4Vh2Wo+ udy6trqu+jMxGxZKRQsEOcPoV7AVgeykp6u4YbxkSUMrWWethE6lT6tClJQQF7HDhu/YK+LrtbnQh /9HXBE6z0FxRo59y6XzA==; 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Thu, 9 Jun 2022 13:06:27 +0000 (UTC) Date: Thu, 9 Jun 2022 15:06:00 +0200 From: Petr Mladek To: Peter Zijlstra Cc: ink@jurassic.park.msu.ru, mattst88@gmail.com, vgupta@kernel.org, linux@armlinux.org.uk, ulli.kroll@googlemail.com, linus.walleij@linaro.org, shawnguo@kernel.org, Sascha Hauer , kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, tony@atomide.com, khilman@kernel.org, catalin.marinas@arm.com, will@kernel.org, guoren@kernel.org, bcain@quicinc.com, chenhuacai@kernel.org, kernel@xen0n.name, geert@linux-m68k.org, sammy@sammy.net, monstr@monstr.eu, tsbogend@alpha.franken.de, dinguyen@kernel.org, jonas@southpole.se, stefan.kristiansson@saunalahti.fi, shorne@gmail.com, James.Bottomley@hansenpartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, richard@nod.at, anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, acme@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, namhyung@kernel.org, jgross@suse.com, srivatsa@csail.mit.edu, amakhalov@vmware.com, pv-drivers@vmware.com, boris.ostrovsky@oracle.com, chris@zankel.net, jcmvbkbc@gmail.com, rafael@kernel.org, lenb@kernel.org, pavel@ucw.cz, gregkh@linuxfoundation.org, mturquette@baylibre.com, sboyd@kernel.org, daniel.lezcano@linaro.org, lpieralisi@kernel.org, sudeep.holla@arm.com, agross@kernel.org, bjorn.andersson@linaro.org, anup@brainfault.org, thierry.reding@gmail.com, jonathanh@nvidia.com, jacob.jun.pan@linux.intel.com, Arnd Bergmann , yury.norov@gmail.com, andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk, rostedt@goodmis.org, senozhatsky@chromium.org, john.ogness@linutronix.de, paulmck@kernel.org, frederic@kernel.org, quic_neeraju@quicinc.com, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, jpoimboe@kernel.org, linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-perf-users@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, linux-xtensa@linux-xtensa.org, linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, linux-clk@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-arch@vger.kernel.org, rcu@vger.kernel.org Subject: Re: [PATCH 24/36] printk: Remove trace_.*_rcuidle() usage Message-ID: References: <20220608142723.103523089@infradead.org> <20220608144517.444659212@infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220609_060630_927142_0FA331B6 X-CRM114-Status: GOOD ( 21.74 ) X-BeenThere: linux-snps-arc@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux on Synopsys ARC Processors List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+linux-snps-arc=archiver.kernel.org@lists.infradead.org On Thu 2022-06-09 12:02:04, Peter Zijlstra wrote: > On Thu, Jun 09, 2022 at 11:16:46AM +0200, Petr Mladek wrote: > > On Wed 2022-06-08 16:27:47, Peter Zijlstra wrote: > > > The problem, per commit fc98c3c8c9dc ("printk: use rcuidle console > > > tracepoint"), was printk usage from the cpuidle path where RCU was > > > already disabled. > > > > > Does this "prevent" calling printk() a safe way in code with > > RCU disabled? > > On x86_64, yes. Other architectures, less so. > > Specifically, the objtool noinstr validation pass will warn at build > time (DEBUG_ENTRY=y) if any noinstr/cpuidle code does a call to > non-vetted code like printk(). > > At the same time; there's a few hacks that allow WARN to work, but > mostly if you hit WARN in entry/noinstr you get to keep the pieces in > any case. > > On other architecture we'll need to rely on runtime coverage with > PROVE_RCU. That is, if a splat like in the above mentioned commit > happens again, we'll need to fix it by adjusting the callchain, not by > mucking about with RCU state. Makes sense. Feel free to use for this patch: Acked-by: Petr Mladek > > Therefore if this patch allows to remove some tricky tracing > > code then it might be worth it. But if trace_console_rcuidle() > > variant is still going to be available then I would keep using it. > > My ultimate goal is to delete trace_.*_rcuidle() and RCU_NONIDLE() > entirely. We're close, but not quite there yet. I keep my fingers crossed. Best Regards, Petr _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc 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 Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 42A94C43334 for ; Thu, 9 Jun 2022 13:06:35 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id D410C840C2; Thu, 9 Jun 2022 13:06:34 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id hcDpC5mQ4Fvj; Thu, 9 Jun 2022 13:06:34 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp1.osuosl.org (Postfix) with ESMTPS id 6F3D78409F; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Thu 2022-06-09 12:02:04, Peter Zijlstra wrote: > On Thu, Jun 09, 2022 at 11:16:46AM +0200, Petr Mladek wrote: > > On Wed 2022-06-08 16:27:47, Peter Zijlstra wrote: > > > The problem, per commit fc98c3c8c9dc ("printk: use rcuidle console > > > tracepoint"), was printk usage from the cpuidle path where RCU was > > > already disabled. > > > > > Does this "prevent" calling printk() a safe way in code with > > RCU disabled? > > On x86_64, yes. Other architectures, less so. > > Specifically, the objtool noinstr validation pass will warn at build > time (DEBUG_ENTRY=y) if any noinstr/cpuidle code does a call to > non-vetted code like printk(). > > At the same time; there's a few hacks that allow WARN to work, but > mostly if you hit WARN in entry/noinstr you get to keep the pieces in > any case. > > On other architecture we'll need to rely on runtime coverage with > PROVE_RCU. That is, if a splat like in the above mentioned commit > happens again, we'll need to fix it by adjusting the callchain, not by > mucking about with RCU state. Makes sense. Feel free to use for this patch: Acked-by: Petr Mladek > > Therefore if this patch allows to remove some tricky tracing > > code then it might be worth it. But if trace_console_rcuidle() > > variant is still going to be available then I would keep using it. > > My ultimate goal is to delete trace_.*_rcuidle() and RCU_NONIDLE() > entirely. We're close, but not quite there yet. I keep my fingers crossed. Best Regards, Petr _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization 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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DD62FC43334 for ; Fri, 10 Jun 2022 15:33:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; 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h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=fQ7/fX+AXX7RSe4KqEkRum0uc4vC19BTUP6nq2wTOec=; b=o28ZaXYpRsbDNeH7DdY3dJH3Fnc3dlxZT8L+x/2aFmo5tE4BAEDzQGW4+i3DDhNGrDHekt G23+f/oOyTepRO03yIh1gixSASehX2C07pg1fm0i3R3KDgn22PhYw8V9jvCq8nE2YIN+/O p3FQSqV1HR0kVCZZzDry3RvUltYRjYI= Received: from suse.cz (unknown [10.100.208.146]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id CEE382C141; Thu, 9 Jun 2022 13:06:27 +0000 (UTC) Date: Thu, 9 Jun 2022 15:06:00 +0200 From: Petr Mladek To: Peter Zijlstra Cc: ink@jurassic.park.msu.ru, mattst88@gmail.com, vgupta@kernel.org, linux@armlinux.org.uk, ulli.kroll@googlemail.com, linus.walleij@linaro.org, shawnguo@kernel.org, Sascha Hauer , kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, tony@atomide.com, khilman@kernel.org, catalin.marinas@arm.com, will@kernel.org, guoren@kernel.org, bcain@quicinc.com, chenhuacai@kernel.org, kernel@xen0n.name, geert@linux-m68k.org, sammy@sammy.net, monstr@monstr.eu, tsbogend@alpha.franken.de, dinguyen@kernel.org, jonas@southpole.se, stefan.kristiansson@saunalahti.fi, shorne@gmail.com, James.Bottomley@hansenpartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, richard@nod.at, anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, acme@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, namhyung@kernel.org, jgross@suse.com, srivatsa@csail.mit.edu, amakhalov@vmware.com, pv-drivers@vmware.com, boris.ostrovsky@oracle.com, chris@zankel.net, jcmvbkbc@gmail.com, rafael@kernel.org, lenb@kernel.org, pavel@ucw.cz, gregkh@linuxfoundation.org, mturquette@baylibre.com, sboyd@kernel.org, daniel.lezcano@linaro.org, lpieralisi@kernel.org, sudeep.holla@arm.com, agross@kernel.org, bjorn.andersson@linaro.org, anup@brainfault.org, thierry.reding@gmail.com, jonathanh@nvidia.com, jacob.jun.pan@linux.intel.com, Arnd Bergmann , yury.norov@gmail.com, andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk, rostedt@goodmis.org, senozhatsky@chromium.org, john.ogness@linutronix.de, paulmck@kernel.org, frederic@kernel.org, quic_neeraju@quicinc.com, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, jpoimboe@kernel.org, linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-perf-users@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, linux-xtensa@linux-xtensa.org, linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, linux-clk@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-arch@vger.kernel.org, rcu@vger.kernel.org Subject: Re: [PATCH 24/36] printk: Remove trace_.*_rcuidle() usage Message-ID: References: <20220608142723.103523089@infradead.org> <20220608144517.444659212@infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220609_060630_927142_0FA331B6 X-CRM114-Status: GOOD ( 21.74 ) X-Mailman-Approved-At: Fri, 10 Jun 2022 08:33:13 -0700 X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Thu 2022-06-09 12:02:04, Peter Zijlstra wrote: > On Thu, Jun 09, 2022 at 11:16:46AM +0200, Petr Mladek wrote: > > On Wed 2022-06-08 16:27:47, Peter Zijlstra wrote: > > > The problem, per commit fc98c3c8c9dc ("printk: use rcuidle console > > > tracepoint"), was printk usage from the cpuidle path where RCU was > > > already disabled. > > > > > Does this "prevent" calling printk() a safe way in code with > > RCU disabled? > > On x86_64, yes. Other architectures, less so. > > Specifically, the objtool noinstr validation pass will warn at build > time (DEBUG_ENTRY=y) if any noinstr/cpuidle code does a call to > non-vetted code like printk(). > > At the same time; there's a few hacks that allow WARN to work, but > mostly if you hit WARN in entry/noinstr you get to keep the pieces in > any case. > > On other architecture we'll need to rely on runtime coverage with > PROVE_RCU. That is, if a splat like in the above mentioned commit > happens again, we'll need to fix it by adjusting the callchain, not by > mucking about with RCU state. Makes sense. Feel free to use for this patch: Acked-by: Petr Mladek > > Therefore if this patch allows to remove some tricky tracing > > code then it might be worth it. But if trace_console_rcuidle() > > variant is still going to be available then I would keep using it. > > My ultimate goal is to delete trace_.*_rcuidle() and RCU_NONIDLE() > entirely. We're close, but not quite there yet. I keep my fingers crossed. Best Regards, Petr _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv 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 Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 486E8C43334 for ; Fri, 10 Jun 2022 11:20:49 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4LKJRg6DXXz3f6B for ; Fri, 10 Jun 2022 21:20:47 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=suse.com header.i=@suse.com header.a=rsa-sha256 header.s=susede1 header.b=o28ZaXYp; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; 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bh=fQ7/fX+AXX7RSe4KqEkRum0uc4vC19BTUP6nq2wTOec=; b=o28ZaXYpRsbDNeH7DdY3dJH3Fnc3dlxZT8L+x/2aFmo5tE4BAEDzQGW4+i3DDhNGrDHekt G23+f/oOyTepRO03yIh1gixSASehX2C07pg1fm0i3R3KDgn22PhYw8V9jvCq8nE2YIN+/O p3FQSqV1HR0kVCZZzDry3RvUltYRjYI= Received: from suse.cz (unknown [10.100.208.146]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id CEE382C141; Thu, 9 Jun 2022 13:06:27 +0000 (UTC) Date: Thu, 9 Jun 2022 15:06:00 +0200 From: Petr Mladek To: Peter Zijlstra Subject: Re: [PATCH 24/36] printk: Remove trace_.*_rcuidle() usage Message-ID: References: <20220608142723.103523089@infradead.org> <20220608144517.444659212@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Mailman-Approved-At: Fri, 10 Jun 2022 21:09:20 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: juri.lelli@redhat.com, rafael@kernel.org, linus.walleij@linaro.org, bsegall@google.com, guoren@kernel.org, pavel@ucw.cz, agordeev@linux.ibm.com, srivatsa@csail.mit.edu, linux-arch@vger.kernel.org, vincent.guittot@linaro.org, chenhuacai@kernel.org, linux-acpi@vger.kernel.org, agross@kernel.org, geert@linux-m68k.org, linux-imx@nxp.com, catalin.marinas@arm.com, xen-devel@lists.xenproject.org, mattst88@gmail.com, borntraeger@linux.ibm.com, mturquette@baylibre.com, sammy@sammy.net, linux-pm@vger.kernel.org, jiangshanlai@gmail.com, Sascha Hauer , linux-um@lists.infradead.org, acme@kernel.org, tglx@linutronix.de, linux-omap@vger.kernel.org, dietmar.eggemann@arm.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, senozhatsky@chromium.org, svens@linux.ibm.com, jolsa@kernel.org, paulus@samba.org, mark.rutland@arm.com, linux-ia64@vger.kernel.org, dave.hansen@linux.intel.com, virtualization@lists.linux-foundation.org, James .Bottomley@hansenpartnership.com, jcmvbkbc@gmail.com, thierry.reding@gmail.com, kernel@xen0n.name, quic_neeraju@quicinc.com, linux-s390@vger.kernel.org, vschneid@redhat.com, john.ogness@linutronix.de, ysato@users.sourceforge.jp, linux-sh@vger.kernel.org, festevam@gmail.com, deller@gmx.de, daniel.lezcano@linaro.org, jonathanh@nvidia.com, mathieu.desnoyers@efficios.com, frederic@kernel.org, lenb@kernel.org, linux-xtensa@linux-xtensa.org, kernel@pengutronix.de, gor@linux.ibm.com, linux-arm-msm@vger.kernel.org, linux-alpha@vger.kernel.org, linux-m68k@lists.linux-m68k.org, shorne@gmail.com, linux-arm-kernel@lists.infradead.org, chris@zankel.net, sboyd@kernel.org, dinguyen@kernel.org, bristot@redhat.com, alexander.shishkin@linux.intel.com, lpieralisi@kernel.org, linux@rasmusvillemoes.dk, joel@joelfernandes.org, will@kernel.org, boris.ostrovsky@oracle.com, khilman@kernel.org, linux-csky@vger.kernel.org, pv-drivers@vmware.com, linux-snps-arc@lists.infradead.org, mgorman@suse.de, jacob.jun.p an@linux.intel.com, Arnd Bergmann , ul li.kroll@googlemail.com, vgupta@kernel.org, linux-clk@vger.kernel.org, josh@joshtriplett.org, rostedt@goodmis.org, rcu@vger.kernel.org, bp@alien8.de, bcain@quicinc.com, tsbogend@alpha.franken.de, linux-parisc@vger.kernel.org, sudeep.holla@arm.com, shawnguo@kernel.org, davem@davemloft.net, dalias@libc.org, tony@atomide.com, amakhalov@vmware.com, bjorn.andersson@linaro.org, hpa@zytor.com, sparclinux@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-riscv@lists.infradead.org, anton.ivanov@cambridgegreys.com, jonas@southpole.se, yury.norov@gmail.com, richard@nod.at, x86@kernel.org, linux@armlinux.org.uk, mingo@redhat.com, aou@eecs.berkeley.edu, paulmck@kernel.org, hca@linux.ibm.com, stefan.kristiansson@saunalahti.fi, openrisc@lists.librecores.org, paul.walmsley@sifive.com, linux-tegra@vger.kernel.org, namhyung@kernel.org, andriy.shevchenko@linux.intel.com, jpoimboe@kernel.org, jgross@suse.com, monstr@monstr.eu, linux-mips@vger.kernel.org, palmer@dabbelt.com, anup@brainfault.org, ink@ jurassic.park.msu.ru, johannes@sipsolutions.net, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thu 2022-06-09 12:02:04, Peter Zijlstra wrote: > On Thu, Jun 09, 2022 at 11:16:46AM +0200, Petr Mladek wrote: > > On Wed 2022-06-08 16:27:47, Peter Zijlstra wrote: > > > The problem, per commit fc98c3c8c9dc ("printk: use rcuidle console > > > tracepoint"), was printk usage from the cpuidle path where RCU was > > > already disabled. > > > > > Does this "prevent" calling printk() a safe way in code with > > RCU disabled? > > On x86_64, yes. Other architectures, less so. > > Specifically, the objtool noinstr validation pass will warn at build > time (DEBUG_ENTRY=y) if any noinstr/cpuidle code does a call to > non-vetted code like printk(). > > At the same time; there's a few hacks that allow WARN to work, but > mostly if you hit WARN in entry/noinstr you get to keep the pieces in > any case. > > On other architecture we'll need to rely on runtime coverage with > PROVE_RCU. That is, if a splat like in the above mentioned commit > happens again, we'll need to fix it by adjusting the callchain, not by > mucking about with RCU state. Makes sense. Feel free to use for this patch: Acked-by: Petr Mladek > > Therefore if this patch allows to remove some tricky tracing > > code then it might be worth it. But if trace_console_rcuidle() > > variant is still going to be available then I would keep using it. > > My ultimate goal is to delete trace_.*_rcuidle() and RCU_NONIDLE() > entirely. We're close, but not quite there yet. I keep my fingers crossed. Best Regards, Petr 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 Received: from mail.librecores.org (lists.librecores.org [88.198.125.70]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0A7CAC433EF for ; Sat, 11 Jun 2022 21:54:10 +0000 (UTC) Received: from [172.31.1.100] (localhost.localdomain [127.0.0.1]) by mail.librecores.org (Postfix) with ESMTP id 254CE247CB; Sat, 11 Jun 2022 23:54:08 +0200 (CEST) Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by mail.librecores.org (Postfix) with ESMTPS id 66DB1242D4 for ; Thu, 9 Jun 2022 15:06:29 +0200 (CEST) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id EEA1421F3C; Thu, 9 Jun 2022 13:06:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1654779989; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=fQ7/fX+AXX7RSe4KqEkRum0uc4vC19BTUP6nq2wTOec=; b=o28ZaXYpRsbDNeH7DdY3dJH3Fnc3dlxZT8L+x/2aFmo5tE4BAEDzQGW4+i3DDhNGrDHekt G23+f/oOyTepRO03yIh1gixSASehX2C07pg1fm0i3R3KDgn22PhYw8V9jvCq8nE2YIN+/O p3FQSqV1HR0kVCZZzDry3RvUltYRjYI= Received: from suse.cz (unknown [10.100.208.146]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id CEE382C141; Thu, 9 Jun 2022 13:06:27 +0000 (UTC) Date: Thu, 9 Jun 2022 15:06:00 +0200 From: Petr Mladek To: Peter Zijlstra Subject: Re: [PATCH 24/36] printk: Remove trace_.*_rcuidle() usage Message-ID: References: <20220608142723.103523089@infradead.org> <20220608144517.444659212@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Mailman-Approved-At: Sat, 11 Jun 2022 23:54:06 +0200 X-BeenThere: openrisc@lists.librecores.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: Discussion around the OpenRISC processor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: juri.lelli@redhat.com, rafael@kernel.org, benh@kernel.crashing.org, linus.walleij@linaro.org, bsegall@google.com, guoren@kernel.org, pavel@ucw.cz, agordeev@linux.ibm.com, srivatsa@csail.mit.edu, linux-arch@vger.kernel.org, vincent.guittot@linaro.org, mpe@ellerman.id.au, chenhuacai@kernel.org, linux-acpi@vger.kernel.org, agross@kernel.org, linux-imx@nxp.com, catalin.marinas@arm.com, xen-devel@lists.xenproject.org, mattst88@gmail.com, borntraeger@linux.ibm.com, mturquette@baylibre.com, sammy@sammy.net, linux-pm@vger.kernel.org, jiangshanlai@gmail.com, Sascha Hauer , linux-um@lists.infradead.org, acme@kernel.org, tglx@linutronix.de, linux-omap@vger.kernel.org, dietmar.eggemann@arm.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, senozhatsky@chromium.org, svens@linux.ibm.com, jolsa@kernel.org, paulus@samba.org, mark.rutland@arm.com, linux-ia64@vger.kernel.org, dave.hansen@linux.intel.com, virtualization@lists.linux-foundation.org, James.Bottomley@hansenpartnership.com, jcmvbkbc@gmail.com, thierry.reding@gmail.com, kernel@xen0n.name, quic_neeraju@quicinc.com, linux-s390@vger.kernel.org, vschneid@redhat.com, john.ogness@linutronix.de, ysato@users.sourceforge.jp, linux-sh@vger.kernel.org, festevam@gmail.com, deller@gmx.de, daniel.lezcano@linaro.org, jonathanh@nvidia.com, mathieu.desnoyers@efficios.com, frederic@kernel.org, lenb@kernel.org, linux-xtensa@linux-xtensa.org, kernel@pengutronix.de, gor@linux.ibm.com, linux-arm-msm@vger.kernel.org, linux-alpha@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-arm-kernel@lists.infradead.org, chris@zankel.net, sboyd@kernel.org, dinguyen@kernel.org, bristot@redhat.com, alexander.shishkin@linux.intel.com, lpieralisi@kernel.org, linux@rasmusvillemoes.dk, joel@joelfernandes.org, will@kernel.org, boris.ostrovsky@oracle.com, khilman@kernel.org, linux-csky@vger.kernel.org, pv-drivers@vmware.com, linux-snps-arc@lists.infradead.org, mgorman@suse.de, jacob.jun.pan@linux.intel.com, Arnd Bergmann , ulli.kroll@googlemail.com, vgupta@kernel.org, linux-clk@vger.kernel.org, josh@joshtriplett.org, rostedt@goodmis.org, rcu@vger.kernel.org, bp@alien8.de, bcain@quicinc.com, tsbogend@alpha.franken.de, linux-parisc@vger.kernel.org, sudeep.holla@arm.com, shawnguo@kernel.org, davem@davemloft.net, dalias@libc.org, tony@atomide.com, amakhalov@vmware.com, bjorn.andersson@linaro.org, hpa@zytor.com, sparclinux@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-riscv@lists.infradead.org, anton.ivanov@cambridgegreys.com, jonas@southpole.se, yury.norov@gmail.com, richard@nod.at, x86@kernel.org, linux@armlinux.org.uk, mingo@redhat.com, aou@eecs.berkeley.edu, paulmck@kernel.org, hca@linux.ibm.com, openrisc@lists.librecores.org, paul.walmsley@sifive.com, linux-tegra@vger.kernel.org, namhyung@kernel.org, andriy.shevchenko@linux.intel.com, jpoimboe@kernel.org, jgross@suse.com, monstr@monstr.eu, linux-mips@vger.kernel.org, palmer@dabbelt.com, anup@brainfault.org, ink@jurassic.park.msu.ru, johannes@sipsolutions.net, linuxppc-dev@lists.ozlabs.org Errors-To: openrisc-bounces@lists.librecores.org Sender: "OpenRISC" On Thu 2022-06-09 12:02:04, Peter Zijlstra wrote: > On Thu, Jun 09, 2022 at 11:16:46AM +0200, Petr Mladek wrote: > > On Wed 2022-06-08 16:27:47, Peter Zijlstra wrote: > > > The problem, per commit fc98c3c8c9dc ("printk: use rcuidle console > > > tracepoint"), was printk usage from the cpuidle path where RCU was > > > already disabled. > > > > > Does this "prevent" calling printk() a safe way in code with > > RCU disabled? > > On x86_64, yes. Other architectures, less so. > > Specifically, the objtool noinstr validation pass will warn at build > time (DEBUG_ENTRY=y) if any noinstr/cpuidle code does a call to > non-vetted code like printk(). > > At the same time; there's a few hacks that allow WARN to work, but > mostly if you hit WARN in entry/noinstr you get to keep the pieces in > any case. > > On other architecture we'll need to rely on runtime coverage with > PROVE_RCU. That is, if a splat like in the above mentioned commit > happens again, we'll need to fix it by adjusting the callchain, not by > mucking about with RCU state. Makes sense. Feel free to use for this patch: Acked-by: Petr Mladek > > Therefore if this patch allows to remove some tricky tracing > > code then it might be worth it. But if trace_console_rcuidle() > > variant is still going to be available then I would keep using it. > > My ultimate goal is to delete trace_.*_rcuidle() and RCU_NONIDLE() > entirely. We're close, but not quite there yet. I keep my fingers crossed. Best Regards, Petr From mboxrd@z Thu Jan 1 00:00:00 1970 From: Petr Mladek Date: Thu, 09 Jun 2022 13:06:00 +0000 Subject: Re: [PATCH 24/36] printk: Remove trace_.*_rcuidle() usage Message-Id: List-Id: References: <20220608142723.103523089@infradead.org> <20220608144517.444659212@infradead.org> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Peter Zijlstra Cc: ink@jurassic.park.msu.ru, mattst88@gmail.com, vgupta@kernel.org, linux@armlinux.org.uk, ulli.kroll@googlemail.com, linus.walleij@linaro.org, shawnguo@kernel.org, Sascha Hauer , kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, tony@atomide.com, khilman@kernel.org, catalin.marinas@arm.com, will@kernel.org, guoren@kernel.org, bcain@quicinc.com, chenhuacai@kernel.org, kernel@xen0n.name, geert@linux-m68k.org, sammy@sammy.net, monstr@monstr.eu, tsbogend@alpha.franken.de, dinguyen@kernel.org, jonas@southpole.se, stefan.kristiansson@saunalahti.fi, shorne@gmail.com, James.Bottomley@hansenpartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, richard@nod.at, anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, acme@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, namhyung@kernel.org, jgross@suse.com, srivatsa@csail.mit.edu, amakhalov@vmware.com, pv-drivers@vmware.com, boris.ostrovsky@oracle.com, chris@zankel.net, jcmvbkbc@gmail.com, rafael@kernel.org, lenb@kernel.org, pavel@ucw.cz, gregkh@linuxfoundation.org, mturquette@baylibre.com, sboyd@kernel.org, daniel.lezcano@linaro.org, lpieralisi@kernel.org, sudeep.holla@arm.com, agross@kernel.org, bjorn.andersson@linaro.org, anup@brainfault.org, thierry.reding@gmail.com, jonathanh@nvidia.com, jacob.jun.pan@linux.intel.com, Arnd Bergmann , yury.norov@gmail.com, andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk, rostedt@goodmis.org, senozhatsky@chromium.org, john.ogness@linutronix.de, paulmck@kernel.org, frederic@kernel.org, quic_neeraju@quicinc.com, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, jpoimboe@kernel.org, linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-perf-users@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, linux-xtensa@linux-xtensa.org, linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, linux-clk@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-arch@vger.kernel.org, rcu@vger.kernel.org On Thu 2022-06-09 12:02:04, Peter Zijlstra wrote: > On Thu, Jun 09, 2022 at 11:16:46AM +0200, Petr Mladek wrote: > > On Wed 2022-06-08 16:27:47, Peter Zijlstra wrote: > > > The problem, per commit fc98c3c8c9dc ("printk: use rcuidle console > > > tracepoint"), was printk usage from the cpuidle path where RCU was > > > already disabled. > > > > > Does this "prevent" calling printk() a safe way in code with > > RCU disabled? > > On x86_64, yes. Other architectures, less so. > > Specifically, the objtool noinstr validation pass will warn at build > time (DEBUG_ENTRY=y) if any noinstr/cpuidle code does a call to > non-vetted code like printk(). > > At the same time; there's a few hacks that allow WARN to work, but > mostly if you hit WARN in entry/noinstr you get to keep the pieces in > any case. > > On other architecture we'll need to rely on runtime coverage with > PROVE_RCU. That is, if a splat like in the above mentioned commit > happens again, we'll need to fix it by adjusting the callchain, not by > mucking about with RCU state. Makes sense. Feel free to use for this patch: Acked-by: Petr Mladek > > Therefore if this patch allows to remove some tricky tracing > > code then it might be worth it. But if trace_console_rcuidle() > > variant is still going to be available then I would keep using it. > > My ultimate goal is to delete trace_.*_rcuidle() and RCU_NONIDLE() > entirely. We're close, but not quite there yet. I keep my fingers crossed. Best Regards, Petr From mboxrd@z Thu Jan 1 00:00:00 1970 From: Petr Mladek Subject: Re: [PATCH 24/36] printk: Remove trace_.*_rcuidle() usage Date: Thu, 9 Jun 2022 15:06:00 +0200 Message-ID: References: <20220608142723.103523089@infradead.org> <20220608144517.444659212@infradead.org> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1654779989; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=fQ7/fX+AXX7RSe4KqEkRum0uc4vC19BTUP6nq2wTOec=; b=o28ZaXYpRsbDNeH7DdY3dJH3Fnc3dlxZT8L+x/2aFmo5tE4BAEDzQGW4+i3DDhNGrDHekt G23+f/oOyTepRO03yIh1gixSASehX2C07pg1fm0i3R3KDgn22PhYw8V9jvCq8nE2YIN+/O p3FQSqV1HR0kVCZZzDry3RvUltYRjYI= Content-Disposition: inline In-Reply-To: List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Peter Zijlstra Cc: ink@jurassic.park.msu.ru, mattst88@gmail.com, vgupta@kernel.org, linux@armlinux.org.uk, ulli.kroll@googlemail.com, linus.walleij@linaro.org, shawnguo@kernel.org, Sascha Hauer , kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, tony@atomide.com, khilman@kernel.org, catalin.marinas@arm.com, will@kernel.org, guoren@kernel.org, bcain@quicinc.com, chenhuacai@kernel.org, kernel@xen0n.name, geert@linux-m68k.org, sammy@sammy.net, monstr@monstr.eu, tsbogend@alpha.franken.de, dinguyen@kernel.org, jonas@southpole.se, stefan.kristiansson@saunalahti.fi, shorne@gmail.com, James.Bottomley@hansenpartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, On Thu 2022-06-09 12:02:04, Peter Zijlstra wrote: > On Thu, Jun 09, 2022 at 11:16:46AM +0200, Petr Mladek wrote: > > On Wed 2022-06-08 16:27:47, Peter Zijlstra wrote: > > > The problem, per commit fc98c3c8c9dc ("printk: use rcuidle console > > > tracepoint"), was printk usage from the cpuidle path where RCU was > > > already disabled. > > > > > Does this "prevent" calling printk() a safe way in code with > > RCU disabled? > > On x86_64, yes. Other architectures, less so. > > Specifically, the objtool noinstr validation pass will warn at build > time (DEBUG_ENTRY=y) if any noinstr/cpuidle code does a call to > non-vetted code like printk(). > > At the same time; there's a few hacks that allow WARN to work, but > mostly if you hit WARN in entry/noinstr you get to keep the pieces in > any case. > > On other architecture we'll need to rely on runtime coverage with > PROVE_RCU. That is, if a splat like in the above mentioned commit > happens again, we'll need to fix it by adjusting the callchain, not by > mucking about with RCU state. Makes sense. Feel free to use for this patch: Acked-by: Petr Mladek > > Therefore if this patch allows to remove some tricky tracing > > code then it might be worth it. But if trace_console_rcuidle() > > variant is still going to be available then I would keep using it. > > My ultimate goal is to delete trace_.*_rcuidle() and RCU_NONIDLE() > entirely. We're close, but not quite there yet. I keep my fingers crossed. Best Regards, Petr