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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43F6FC64ED6 for ; Fri, 17 Feb 2023 19:38:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 646636B0071; Fri, 17 Feb 2023 14:38:43 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5F6D96B0072; Fri, 17 Feb 2023 14:38:43 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4BE2E6B0073; Fri, 17 Feb 2023 14:38:43 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 3DDAF6B0071 for ; Fri, 17 Feb 2023 14:38:43 -0500 (EST) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 10416C097A for ; Fri, 17 Feb 2023 19:38:43 +0000 (UTC) X-FDA: 80477796126.21.4ADBD46 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf07.hostedemail.com (Postfix) with ESMTP id 3C9654000B for ; Fri, 17 Feb 2023 19:38:39 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=j6Mg8xar; spf=none (imf07.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1676662720; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=IVvNxzJ/MYYOfgoLuHJ17dzipL9pSi1JZZiiDTevKw0=; b=yfJDFj5sZKs+kwic3KYEWrgKuu1/eabw14zCfSvmb6O5zxxpdBj3YX53gNzi6kdMgC6VJM GfXHuXohOoCymgxv+HPiJVDnMlr559aUcOMBB49FIhUyl7B6kB/L+2uYL9uOzWQOQVFIec F3A4jSB2wl1C3ayjy8bbFjqBROgIJMk= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=j6Mg8xar; spf=none (imf07.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1676662720; a=rsa-sha256; cv=none; b=GhGONCWtdjzjMK4LZGrURo/ni241WxW3iyu7nZpt/ByV9JNBtFx5qUEoXjbG7o59rOIHdu n8TanOZEbhOcbOlSjAX7irPkO3dchDU0e5yuVoMBNZ7Y+tk4pXXNKMMgMFdL8gNQJUDUJd IgpzmfhrufQ/pFxAjDgfPdKNKhShp2s= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=IVvNxzJ/MYYOfgoLuHJ17dzipL9pSi1JZZiiDTevKw0=; b=j6Mg8xarwRuLOAkt6xKfjfU+GK VuWVsDRwqRFW+Xenyylnnk6wTFhc1zFSnWzxWAoHU49KB4fRExFfdmsPS5RsBfviEcuPFC921uy9L 9Hr5l4tCsdd9Mq+L8RZF7yj/X/ZUoguJMzXh4E+DW5BZfGyC9TiwaeCw3IYOezS5GnfcDGRR7PbnR w6QDZ0rv8txqYW+za0a08qmt10QZ9Bqd/tQnWEBxHjktV8S5RQJbzI15mCnADRRpLgymrltXhFjdu 7F4orbZyHkHAaatKo/SxKXMbWgMIeW84rfHeKuXL/DWQ8GPnYaXuMHnsnvHDCYR6pU7RasGrsMjWz mNCsdhfg==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pT6YZ-009Znz-3q; Fri, 17 Feb 2023 19:38:07 +0000 Date: Fri, 17 Feb 2023 19:38:07 +0000 From: Matthew Wilcox To: Danilo Krummrich Cc: airlied@gmail.com, daniel@ffwll.ch, tzimmermann@suse.de, mripard@kernel.org, corbet@lwn.net, christian.koenig@amd.com, bskeggs@redhat.com, Liam.Howlett@oracle.com, matthew.brost@intel.com, boris.brezillon@collabora.com, alexdeucher@gmail.com, ogabbay@kernel.org, bagasdotme@gmail.com, jason@jlekstrand.net, dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH drm-next v2 04/16] maple_tree: add flag MT_FLAGS_LOCK_NONE Message-ID: References: <20230217134422.14116-1-dakr@redhat.com> <20230217134422.14116-5-dakr@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230217134422.14116-5-dakr@redhat.com> X-Rspamd-Queue-Id: 3C9654000B X-Stat-Signature: wq916c5cnjgqratqwyc8o4xn81nzid4c X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1676662718-380569 X-HE-Meta: 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 68wP3l4K EUni08ZlpUdsyaNPu1SJmelh1wWG+5kv/cPy1UDt1HmfpP7TDY9lRJYejDbT+VGoTh0V7c1keawWp52a0ZRc7tRK9EO/x7Z/4mgfPWsVw2m2bbvR6vmM1x4sFYFC7TR0SPlt0WcvL5UkbkGlIYcjT2WNMAG/N554ekLdRwfz4JXXAh3L/04YiELYyKurXc43oYEDBymVMqswiHkM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Feb 17, 2023 at 02:44:10PM +0100, Danilo Krummrich wrote: > Generic components making use of the maple tree (such as the > DRM GPUVA Manager) delegate the responsibility of ensuring mutual > exclusion to their users. > > While such components could inherit the concept of an external lock, > some users might just serialize the access to the component and hence to > the internal maple tree. > > In order to allow such use cases, add a new flag MT_FLAGS_LOCK_NONE to > indicate not to do any internal lockdep checks. I'm really against this change. First, we really should check that users have their locking right. It's bitten us so many times when they get it wrong. Second, having a lock allows us to defragment the slab cache. The patches to do that haven't gone anywhere recently, but if we drop the requirement now, we'll never be able to compact ranges of memory that have slabs allocated to them.