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 53DE0C433EF for ; Fri, 17 Jun 2022 16:53:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1383481AbiFQQxX (ORCPT ); Fri, 17 Jun 2022 12:53:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58950 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1383455AbiFQQxC (ORCPT ); Fri, 17 Jun 2022 12:53:02 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 45B095A0A1 for ; Fri, 17 Jun 2022 09:51:52 -0700 (PDT) Date: Fri, 17 Jun 2022 18:51:48 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1655484710; h=from:from:reply-to:subject:subject: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=UykvkKuHPgfnuKIJnIaYfKgo9S8iB+wmFcj7vk45wVs=; b=eUu/qClCX/d2AouxGZPJTmu48AdbHUOAEqK6i7LTOzrgE4GEiltOUP/aJutgp44nPnjM1S ulO0fZvQYiVcMfcod60L0fl3em63i+QghmCscjAvwGb0MsWcIiu7iqKCZEdO+OY50UIAWi Fzew3TXJ8JyJ31M5UjJ+UNJvMh+wufip+FNl1U45LGUmqJTGg/BwzaScUhjC14W2WpoYGb MWR63P+t6DeKQTXOdDHQPaH/tLPjlCbOP0/O0DhvtyiUkuQZUOA81nEFSDVBi44tlsUGpt q5eEmHXyFIG5Y6DNq8uYSnfp7/EMsOHcfSZWSQnIs/N65YiLViv4oc/1Ii/WQw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1655484710; h=from:from:reply-to:subject:subject: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=UykvkKuHPgfnuKIJnIaYfKgo9S8iB+wmFcj7vk45wVs=; b=+gB6pnNuCevctPh8aBUsQrzYo/gPjJ8DZnaghzrYDBDxO0I6SqrmLwluRFEY2z9zzM9Eox CDKIjQ9JrIzSaRBg== From: Sebastian Andrzej Siewior To: "Jason A. Donenfeld" Cc: Dmitry Vyukov , John Ogness , Geert Uytterhoeven , Marek Szyprowski , Petr Mladek , Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , Linux Kernel Mailing List , Greg Kroah-Hartman , "open list:ARM/Amlogic Meson..." , Theodore Ts'o , Alexander Potapenko , Marco Elver , kasan-dev@googlegroups.com Subject: Re: [PATCH printk v5 1/1] printk: extend console_lock for per-console locking Message-ID: References: <87fslyv6y3.fsf@jogness.linutronix.de> <51dfc4a0-f6cf-092f-109f-a04eeb240655@samsung.com> <87k0b6blz2.fsf@jogness.linutronix.de> <32bba8f8-dec7-78aa-f2e5-f62928412eda@samsung.com> <87y1zkkrjy.fsf@jogness.linutronix.de> <87fske3wzw.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022-06-09 14:27:11 [+0200], Jason A. Donenfeld wrote: > Hi Dmitry, > > On Thu, Jun 09, 2022 at 02:18:19PM +0200, Dmitry Vyukov wrote: > > > AFAIK, CONFIG_PROVE_RAW_LOCK_NESTING is useful for teasing out cases > > > where RT's raw spinlocks will nest wrong with RT's sleeping spinlocks. > > > But nobody who wants an RT kernel will be using KFENCE. So this seems > > > like a non-issue? Maybe just add a `depends on !KFENCE` to > > > PROVE_RAW_LOCK_NESTING? > > > > Don't know if there are other good solutions (of similar simplicity). > > Fortunately, I found one that solves things without needing to > compromise on anything: > https://lore.kernel.org/lkml/20220609121709.12939-1-Jason@zx2c4.com/ > > > Btw, should this new CONFIG_PROVE_RAW_LOCK_NESTING be generally > > enabled on testing systems? We don't have it enabled on syzbot. > > Last time I spoke with RT people about this, the goal was eventually to > *always* enable it when lock proving is enabled, but there are too many > bugs and cases now to do that, so it's an opt-in. I might be > misremembering, though, so CC'ing Sebastian in case he wants to chime > in. That is basically still the case. If CONFIG_PROVE_RAW_LOCK_NESTING yells then there will be yelling on PREEMPT_RT, too. We would like to get things fixed ;) Without going through this thread, John is looking at printk and printk triggers a few of those. That is one of reasons why this is not enabled by default. > Jason Sebastian