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 4C2C8C433F5 for ; Thu, 28 Apr 2022 11:05:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345213AbiD1LIq (ORCPT ); Thu, 28 Apr 2022 07:08:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40536 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343934AbiD1LIm (ORCPT ); Thu, 28 Apr 2022 07:08:42 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D63F42F4; Thu, 28 Apr 2022 04:05:24 -0700 (PDT) Date: Thu, 28 Apr 2022 13:05:21 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1651143922; 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=cnxllsTcAyZYtkavIh31owKoz9rJdYEtxB5QbrLOk3k=; b=UGJNInDBPSxA5iy6App+FFqkZE4flLJQY8+rk28YwbJ9klfs7ZSzorXAs9eSBFVfB/7Zwg AXzmj8T2D3pvGVYrTRB65GPr3Cays9X+igoYKxJpOQ6C7JU6szReOzcaAoxl+EXFX2wCB+ PvrAqZ07eM6cY6FyH8kXF8uTzw8KWUN15fNXQtPmwNHlGZgvuwf3RBtRQKbFHYAkfX6EsT DksWdXCyDYDbfpnV1i5/HkLLLYTuhFabqGHvg3oaXU49FfzTVy+QS6kBwrQ1S88Uy3GAZW GH/UTAzrXlO8x1ZmLK4wl91t5KkjqrN5DfSiWZe/GlzwNHTnbDmPa0acLALlrg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1651143922; 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=cnxllsTcAyZYtkavIh31owKoz9rJdYEtxB5QbrLOk3k=; b=seOCzzM5JH2712g7j/mcC/gzYbbNjXx8Or9WsjyDPI1JoCtzFz/hB2js/Mlnsj0CFf+s2N XKv8UdRY3I6eo0BQ== From: Sebastian Andrzej Siewior To: "Fabio M. De Francesco" Cc: Ira Weiny , Andrew Morton , Catalin Marinas , "Matthew Wilcox (Oracle)" , Will Deacon , Peter Collingbourne , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, outreachy@lists.linux.dev, Mike Rapoport Subject: Re: [PATCH v3 1/4] mm/highmem: Fix kernel-doc warnings in highmem*.h Message-ID: References: <20220427183821.1979-1-fmdefrancesco@gmail.com> <20220427183821.1979-2-fmdefrancesco@gmail.com> <2598013.X9hSmTKtgW@leap> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <2598013.X9hSmTKtgW@leap> Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 2022-04-28 12:54:14 [+0200], Fabio M. De Francesco wrote: > No, it's not sufficient because Matthew Wilcox said that something like "It > is the counterpart of kmap_atomic() for unmapping" (or anything similar) is > _not_ what he wants to see. > > Furthermore, a large part of this text has been written by him (I'm talking > of a couple of weeks ago, when this patch was not part of this series - it > was on its own until Ira Weiny asked me to gather 4 patches in one only > series). Sure. > > This indicates the "migration" is disabled for > > !PREEMPT_RT which is not the case. > > I read again how kmap_atomic() is defined. There are lots of 'if' > statements. Only if the code gets to __kmap_local_pfn_prot(), users can be > assured that it unconditionally calls both migrate_disable() and > preempt_disable(). Right, that part. Then keep it. > > So maybe something like > > > > * Unmaps an address previously mapped by kmap_atomic() and re-enables > > * pagefaults, CPU migration (CONFIG_PREEMPT_RT) or preemption > > * (!CONFIG_PREEMPT_RT). Mappings should be unmapped in the reverse > > > > will make it clear. > > I'm starting to think that this level of detail is too much for users who > just need to understand how to use this function as well as > kmap_local_page(). > > I prefer something like the following: > > + * Unmaps an address previously mapped by kmap_atomic() and re-enables > + * pagefaults and possibly also CPU migration and/or preemption. However, > + * users should not count on disable of migration and/or preemption as a > + * side effect of calling kmap_atomic(). Mappings must be unmapped in the > + * reverse [...] > > I'd also like to write the same paragraph for kmap_local_page(). > > What do you think of being less detailed and instead using the text I wrote > above? Sounds perfect. > Thanks, > > Fabio Sebastian