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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 8F5A2C3DA45 for ; Wed, 10 Jul 2024 11:02:47 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 13DEA10E72A; Wed, 10 Jul 2024 11:02:47 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; secure) header.d=linutronix.de header.i=@linutronix.de header.b="0i+BFO8H"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="TnWTzxN7"; dkim-atps=neutral Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6B10910E72A; Wed, 10 Jul 2024 11:02:45 +0000 (UTC) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1720609363; 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=MB5RUz9En8zgRblZi0YlJjmBHs76SzaICxSLYusWtHk=; b=0i+BFO8HLrjhBE23gu5RU+VP//VQGx7vfP0Ussd6Mzs7fmI3MqZqwtO6gVraOzZCvzj5Wt ZdJhW0mKwWTZTg81dyZ+K3lzM/1zbhtUYuxGB1mng0bqo+jpgGLF2H6/rT0TsntP71GQ2X xA1WBNl/6HUoW8WaIwYYqCBZd4j1cZ/XyDqsDmA4H239njnXMnZZVe7XGYV97e9XD965ln Mn31S1LGxBAOCqyVN5OLGvXXRagN+qKfAk8jxP9T6BA/dCb/CA8po7LZypucSu1Px0VM8D 9XiFu+O4p9AjP5OZMqvI8lP7AXbqNZhEcYlkIvW0uC9lPZ9nvDVPKFsQ0h5TWQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1720609363; 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=MB5RUz9En8zgRblZi0YlJjmBHs76SzaICxSLYusWtHk=; b=TnWTzxN7PjYBExaJdixfiCKsoQwmIaEjW23sPMzLsrosGcAODgfoVfcEiLCXyuKTmu3ay6 BNX61qresqLc2bDw== To: Daniel Vetter , DRI Development , LKML Cc: Intel Graphics Development , Daniel Vetter , syzbot+6cebc1af246fe020a2f0@syzkaller.appspotmail.com, Daniel Vetter , stable@vger.kernel.org, Kent Overstreet , Brian Foster , linux-bcachefs@vger.kernel.org, Petr Mladek , Steven Rostedt , Sergey Senozhatsky Subject: Re: [PATCH 2/2] bcachefs: only console_trylock in bch2_print_string_as_lines In-Reply-To: <20240710093120.732208-2-daniel.vetter@ffwll.ch> References: <20240710093120.732208-1-daniel.vetter@ffwll.ch> <20240710093120.732208-2-daniel.vetter@ffwll.ch> Date: Wed, 10 Jul 2024 13:08:42 +0206 Message-ID: <87frsh33xp.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 2024-07-10, Daniel Vetter wrote: > console_lock is the outermost subsystem lock for a lot of subsystems, > which means get/put_user must nest within. Which means it cannot be > acquired somewhere deeply nested in other locks, and most definitely > not while holding fs locks potentially needed to resolve faults. > > console_trylock is the best we can do here. > > Including printk folks since even trylock feels realyl iffy here to > me. Using the console lock here at all is wrong. The console lock does not prevent other CPUs from calling printk() and inserting lines in between. There is no way to guarantee a contiguous ringbuffer block using multiple printk() calls. The console_lock usage should be removed. John Ogness