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 DD2E1C4332F for ; Thu, 14 Dec 2023 15:53:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1573904AbjLNPxN (ORCPT ); Thu, 14 Dec 2023 10:53:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45828 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1573902AbjLNPxJ (ORCPT ); Thu, 14 Dec 2023 10:53:09 -0500 Received: from mail-pl1-x634.google.com (mail-pl1-x634.google.com [IPv6:2607:f8b0:4864:20::634]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20EA0B2; Thu, 14 Dec 2023 07:53:16 -0800 (PST) Received: by mail-pl1-x634.google.com with SMTP id d9443c01a7336-1d37a6926f7so1613755ad.3; Thu, 14 Dec 2023 07:53:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1702569195; x=1703173995; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=wsHrNooczI2aqm3M6rMha8X9i2K4VFA8VCRi3SyFwoo=; b=FqXbUWnUJiI7aXKZASy0ignfqPRr+OW35+ut5Khwl2/153B4u0agDQxDKmT8Uz/f9A ZUivFqbqTWswwc4PGxuP8b2ynvTappWde6zEQWFomoBLomC/35Lq1z5i+4ZwdpbrdvyG eZYLRncsp6SETT8NwJo0DCWsDJLvZx3RLg06kEGRKF1pu3hvEXm4ehVfYym3aj0TrVp6 n/jTnpFGeZ4jk6LVJFGFVk1t3tm1guNSzOW0vZpmvKf81puw1HY864Q2t8Gp0bSVApIB ApQX9xAoKOTxXHz84IqHJuouDjjGhnzL33iqoHaYcXAkA/i9ygJztJ+15KfnAFoD5oKT 0E9w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1702569195; x=1703173995; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=wsHrNooczI2aqm3M6rMha8X9i2K4VFA8VCRi3SyFwoo=; b=FDydoU8csA/0OtxNizVtHf8NUsxzcd8cJqdk3X7hsZ2U0cFFr7zRqn8+pwt0yDDPMj sbrk1fy8FGFOvBJD9KqU0MFKIfGI33iMYE2VmePJtUwEMp7RXSf8jJ3q40R3eRf93TfD 85FWzpVa8EA2p4zNBIYdPW1E8Bn2l33ZHtbKibJekfBMb/B/7vrBCyDYGIuLCL3LXH37 Xaa1sXGtqdv9H2nlq2eCzXboKoKzx3rX26rylET+snWc9yU+BOr0mMDzUqU/0lkiNsqz fot3yBbtLOQr5pNxE7p7YPrSPeb5yifnSY8VKFDL/MaF9i4DK/xyxBjoYIbvi324h90e SkuA== X-Gm-Message-State: AOJu0Yw63xIiP5L5eEzQ/b615KUNl3F8WtyTPQssv1KHuKd/54DlC5Dx /SmjkvUVtYUG4CmSzyc+ldg= X-Google-Smtp-Source: AGHT+IEBo4BdiAYmx3Bc6qTraGpNE0NfuGJQ08CTLfP/Z2iZcEsK4lBPnIOMnDEC9q7AJ2v/ly7UTA== X-Received: by 2002:a17:902:e74e:b0:1d0:b693:ae15 with SMTP id p14-20020a170902e74e00b001d0b693ae15mr6461391plf.43.1702569195474; Thu, 14 Dec 2023 07:53:15 -0800 (PST) Received: from rigel (60-241-235-125.tpgi.com.au. [60.241.235.125]) by smtp.gmail.com with ESMTPSA id u14-20020a170902e80e00b001d0c37a9ccfsm12521675plg.303.2023.12.14.07.53.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Dec 2023 07:53:15 -0800 (PST) Date: Thu, 14 Dec 2023 23:53:10 +0800 From: Kent Gibson To: Andy Shevchenko Cc: linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org, brgl@bgdev.pl, linus.walleij@linaro.org Subject: Re: [PATCH v2 4/5] gpiolib: cdev: reduce locking in gpio_desc_to_lineinfo() Message-ID: References: <20231214095814.132400-1-warthog618@gmail.com> <20231214095814.132400-5-warthog618@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 14, 2023 at 11:46:54PM +0800, Kent Gibson wrote: > On Thu, Dec 14, 2023 at 11:34:44PM +0800, Kent Gibson wrote: > > On Thu, Dec 14, 2023 at 05:27:29PM +0200, Andy Shevchenko wrote: > > > On Thu, Dec 14, 2023 at 11:19:01PM +0800, Kent Gibson wrote: > > > > On Thu, Dec 14, 2023 at 05:10:23PM +0200, Andy Shevchenko wrote: > > > > > On Thu, Dec 14, 2023 at 05:58:13PM +0800, Kent Gibson wrote: > > > > > > Reduce the time holding the gpio_lock by snapshotting the desc flags, > > > > > > rather than testing them individually while holding the lock. > > > > > > > > > > > > Accept that the calculation of the used field is inherently racy, and > > > > > > only check the availability of the line from pinctrl if other checks > > > > > > pass, so avoiding the check for lines that are otherwise in use. > > > > > > ... > > > > > > > > > - spin_lock_irqsave(&gpio_lock, flags); > > > > > > > > > > Shouldn't this be covered by patch 1 (I mean conversion to scoped_guard() > > > > > instead of spinlock)? > > > > > > > > > > > > > Read the cover letter. > > > > Doing that made the change larger, as flags gets removed then restored. > > > > I had also thought the flag tests would get indented then unindented, but > > > > if we use guard() the indentation should remain unchanged. > > > > > > I'm fine with that as I pointed out (have you received that mail? I had > > > problems with my mail server) the dflags is better semantically, so restoration > > > with _different_ name is fine. > > > > > > > I have noted that some of your replies have been delayed, and I can't be sure > > of what I might not've received. I can't say I've seen one that mentions the > > dflags name being preferable. > > > > I prefer the plain flags name, if there is only one flag variable in the > > function. > > > > > > Can do it in 1 if you are happy with the flags declaration being > > > > removed in patch 1 and restored in 4. > > > > > > Definitely. > > > > > > > Ok will re-arrange in v3. > > > > Hang on - patch 4 has to use a scoped_guard(), so are you ok for patch 1 > to introduce a guard(), to avoid changing the indentation, only to > replace it with a scoped_guard(), to perform the tests after releasing > the lock, in patch 4? > Alternatively, I can move patch 4 to the top of the series. Cheers, Kent.