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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 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-Disposition: inline In-Reply-To: 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, linux-arch@vger.kernel.org, vincent.guittot@linaro.org, mpe@ellerman.id.au, 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, 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.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, 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 X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Petr Mladek via Virtualization Reply-To: Petr Mladek Content-Type: text/plain; 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