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 X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1306DC47404 for ; Fri, 11 Oct 2019 20:35:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CB3D62190F for ; Fri, 11 Oct 2019 20:35:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="mD3HMAfY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728894AbfJKUfO (ORCPT ); Fri, 11 Oct 2019 16:35:14 -0400 Received: from mail-pg1-f195.google.com ([209.85.215.195]:35527 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728889AbfJKUfO (ORCPT ); Fri, 11 Oct 2019 16:35:14 -0400 Received: by mail-pg1-f195.google.com with SMTP id p30so6438072pgl.2; Fri, 11 Oct 2019 13:35:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=pw0y3BwMX+I09FeYhYWoZxZsMfpwQC+D3hPGpejxF9c=; b=mD3HMAfYqmZwwaPDcDzJ7S3GANPKaS5D/24iE/S8zvs6k05wi9ECuzfHa0LQgwIHX9 yFc8dxU/I6b+wsT4e5igFuXC2w4Cfpthng9Ti5TO99l00xxjTFNsVv1ibnHKW5jJERbb u9Stn1gMQu1vFLLvEs8A2l+Kw9RPboezSgU5yTsmiWIWUj2Hd4pqcSljF7B6SmCUkr6K SO+LumDYZ7f7/9SVK51PVsU80s4sRuKSPd4KwARv9hZ7vcmvt3YyL2UzyElhTHbU7QbD V+WpIBlxHPLuwB28zabYXnjhjYjVvsg5iy5BNfl8GMM/SqPCYporY95HPS4WnzfXZxh8 VulQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=pw0y3BwMX+I09FeYhYWoZxZsMfpwQC+D3hPGpejxF9c=; b=YlOgexFHsZ5YFi69+q8dHRdqPscdRzkrc9ANefUZuVQtRQqC9/tVweLElC41Ltqero NHqQgydqMoT1FKKRDY9WeVRC1YOJxsNkdUHje/rzH4cfL74EVhHHnBVB279wK3xFpmyq 5lV4pfB6u2oIjD5mUHpF0H9irjuAlKkOp2aoCM2JbJYYAoQK91rvF/NTopPwzACLtGYr 90ggpGpQdy9CVBEWied61BVLGM6eY4XBymOQ3+Vz8HeLU06/WybY+94VkhLkz+V1AsFm uau8Kts1lMenhhV+rkOCKNIRJrB0nNMwUB2jKwRvvjfxouCMMrhKw/14CIdHLpwkQcLP 0C8A== X-Gm-Message-State: APjAAAW3jGJFmZHC6xbBMW//YgJMSS6ekzwIJa0eu95XK/kF9O3ykyMB qZ6mD8uezbeUQyX/orb4b0Y= X-Google-Smtp-Source: APXvYqy7ogWKyhR5VgQoU7Lu3/It78efXlgAsGNKn1s2Ou2EJAjAvymDnrjQKlWHvgtnDwPPTDVXGQ== X-Received: by 2002:a17:90a:8c92:: with SMTP id b18mr19422480pjo.136.1570826112806; Fri, 11 Oct 2019 13:35:12 -0700 (PDT) Received: from dtor-ws ([2620:15c:202:201:3adc:b08c:7acc:b325]) by smtp.gmail.com with ESMTPSA id h70sm9216625pgc.48.2019.10.11.13.35.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Oct 2019 13:35:11 -0700 (PDT) Date: Fri, 11 Oct 2019 13:35:09 -0700 From: Dmitry Torokhov To: Benjamin Tissoires Cc: Andrey Smirnov , "open list:HID CORE LAYER" , Jiri Kosina , Henrik Rydberg , Sam Bazely , "Pierre-Loup A . Griffais" , Austin Palmer , lkml , "3.8+" Subject: Re: [PATCH 1/3] HID: logitech-hidpp: use devres to manage FF private data Message-ID: <20191011203509.GG229325@dtor-ws> References: <20191007051240.4410-1-andrew.smirnov@gmail.com> <20191007051240.4410-2-andrew.smirnov@gmail.com> <20191011182617.GE229325@dtor-ws> <20191011203303.GF229325@dtor-ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191011203303.GF229325@dtor-ws> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Fri, Oct 11, 2019 at 01:33:03PM -0700, Dmitry Torokhov wrote: > On Fri, Oct 11, 2019 at 09:25:52PM +0200, Benjamin Tissoires wrote: > > On Fri, Oct 11, 2019 at 8:26 PM Dmitry Torokhov > > wrote: > > > > > > On Fri, Oct 11, 2019 at 04:52:04PM +0200, Benjamin Tissoires wrote: > > > > Hi Andrey, > > > > > > > > On Mon, Oct 7, 2019 at 7:13 AM Andrey Smirnov wrote: > > > > > > > > > > To simplify resource management in commit that follows as well as to > > > > > save a couple of extra kfree()s and simplify hidpp_ff_deinit() switch > > > > > driver code to use devres to manage the life-cycle of FF private data. > > > > > > > > > > Signed-off-by: Andrey Smirnov > > > > > Cc: Jiri Kosina > > > > > Cc: Benjamin Tissoires > > > > > Cc: Henrik Rydberg > > > > > Cc: Sam Bazely > > > > > Cc: Pierre-Loup A. Griffais > > > > > Cc: Austin Palmer > > > > > Cc: linux-input@vger.kernel.org > > > > > Cc: linux-kernel@vger.kernel.org > > > > > Cc: stable@vger.kernel.org > > > > > > > > This patch doesn't seem to fix any error, is there a reason to send it > > > > to stable? (besides as a dependency of the rest of the series). > > > > > > > > > --- > > > > > drivers/hid/hid-logitech-hidpp.c | 53 +++++++++++++++++--------------- > > > > > 1 file changed, 29 insertions(+), 24 deletions(-) > > > > > > > > > > diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c > > > > > index 0179f7ed77e5..58eb928224e5 100644 > > > > > --- a/drivers/hid/hid-logitech-hidpp.c > > > > > +++ b/drivers/hid/hid-logitech-hidpp.c > > > > > @@ -2079,6 +2079,11 @@ static void hidpp_ff_destroy(struct ff_device *ff) > > > > > struct hidpp_ff_private_data *data = ff->private; > > > > > > > > > > kfree(data->effect_ids); > > > > > > > > Is there any reasons we can not also devm alloc data->effect_ids? > > > > > > > > > + /* > > > > > + * Set private to NULL to prevent input_ff_destroy() from > > > > > + * freeing our devres allocated memory > > > > > > > > Ouch. There is something wrong here: input_ff_destroy() calls > > > > kfree(ff->private), when the data has not been allocated by > > > > input_ff_create(). This seems to lack a little bit of symmetry. > > > > > > Yeah, ff and ff-memless essentially take over the private data assigned > > > to them. They were done before devm and the lifetime of the "private" > > > data pieces was tied to the lifetime of the input device to simplify > > > error handling and teardown. > > > > Yeah, that stealing of the pointer is not good :) > > But OTOH, it helps > > > > > > > > Maybe we should clean it up a bit... I'm open to suggestions. > > > > The problem I had when doing the review was that there is no easy way > > to have a "devm_input_ff_create_()", because the way it's built is > > already "devres-compatible": the destroy gets called by input core. > > I do not think we want devm_input_ff_create() explicitly, I think the > fact that you can "build up" an input device by allocating it, then > adding slots, poller, ff support, etc, and input core cleans it up is > all good. It is just the ownership if the driver-private data block is > not very obvious and is not compatible with allocating via devm. > > > > > So I don't have a good answer to simplify in a transparent manner > > without breaking the API. > > > > > > > > In this case maybe best way is to get rid of hidpp_ff_destroy() and not > > > set ff->private and rely on devm to free the buffers. One can get to > > > device private data from ff methods via input_get_drvdata() since they > > > all (except destroy) are passed input device pointer. > > > > Sounds like a good idea. However, it seems there might be a race when > > removing the workqueue: > > the workqueue gets deleted in hidpp_remove, when the input node will > > be freed by devres, so after the call of hidpp_remove. > > Yeah, well, that is a common issue with mixing devm and normal resources > (and workqueue here is that "normal" resource), and we should either: > > - not use devm > - use devm_add_action_or_reset() to work in custom actions that work > freeing of non-managed resources into devm flow. Actually, there is a door #3: use system workqueue. After all the work that Tejun done on workqueues it is very rare that one actually needs a dedicated workqueue (as works usually execute on one if the system worker threads that are shared with other workqueues anyway). -- Dmitry