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[60.241.235.125]) by smtp.gmail.com with ESMTPSA id nb11-20020a17090b35cb00b0028017a2a8fasm13426949pjb.3.2023.12.14.07.34.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Dec 2023 07:34:49 -0800 (PST) Date: Thu, 14 Dec 2023 23:34:44 +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 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. Cheers, Kent.