linux-kernel - Re: [PATCH v1 0/3] PM: runtime: Wrapper macros for usage counter guards

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Message-ID: <6914fbb5a6ce_1d911001b@dwillia2-mobl4.notmuch>
Date: Wed, 12 Nov 2025 13:27:17 -0800
From: <dan.j.williams@...el.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>, Dhruva Gole <d-gole@...com>,
	Jonathan Cameron <jonathan.cameron@...wei.com>, Frank Li <Frank.Li@....com>
CC: Linux PM <linux-pm@...r.kernel.org>, Linux ACPI
	<linux-acpi@...r.kernel.org>, Takashi Iwai <tiwai@...e.de>, LKML
	<linux-kernel@...r.kernel.org>, Zhang Qilong <zhangqilong3@...wei.com>, "Dan
 Williams" <dan.j.williams@...el.com>, Linux PCI <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <helgaas@...nel.org>, Alex Williamson
	<alex.williamson@...hat.com>
Subject: Re: [PATCH v1 0/3] PM: runtime: Wrapper macros for usage counter
 guards

Rafael J. Wysocki wrote:
> On Wednesday, November 12, 2025 7:39:41 AM CET Dhruva Gole wrote:
> > On Nov 07, 2025 at 19:35:09 +0100, Rafael J. Wysocki wrote:
> > > Hi All,
> > > 
> > > The runtime PM usage counter guards introduced recently:
> > > 
> > > https://lore.kernel.org/linux-pm/6196611.lOV4Wx5bFT@rafael.j.wysocki/
> > > 
> > > and then fixed:
> > > 
> > > https://lore.kernel.org/linux-pm/5943878.DvuYhMxLoT@rafael.j.wysocki/
> > > 
> > > should generally work, but using them feels sort of arcane and cryptic
> > > even though the underlying concept is relatively straightforward.
> > > 
> > > For this reason, runtime PM wrapper macros around ACQUIRE() and
> > > ACQUIRE_ERR() involving the new guards are introduced in this series
> > > (patch [1/3]) and then used in the code already using the guards (patches
> > > [2/3] and [3/3]) to make it look more straightforward.
> > 
> > The patches look okay to me,
> > Reviewed-by: Dhruva Gole <d-gole@...com>
> 
> Thank you and Jonathan for the tags, but since Frank is not convinced, let me
> bounce one more idea off all of you.
> 
> Namely, I think that Frank has a point when he wonders if PM_RUNTIME_ACQUIRE_ERR
> hides too much information and I agree with Jonathan that may be misunderstood,
> so what about defining the wrapper macros so they don't hide the guard variable
> name, like in the patch below?

I had been reluctant about offering an enthusiastic tag on this series
given that information hiding, but with this change:

Reviewed-by: Dan Williams <dan.j.williams@...el.com>

However, I prefer that the scope variable declaration vs usage
(reference) cases should maintain visual separation with an operator,
i.e.:

        PM_RUNTIME_ACQUIRE(dev, pm);
        if (PM_RUNTIME_ACQUIRE_ERR(&pm))
                return -ENXIO;

Otherwise we have a case of different flavors of *_ACQUIRE_ERR
implementing various styles. I initially looked at hiding the '&':

http://lore.kernel.org/681ea7d5ea04b_2a2bb100cf@dwillia2-mobl4.notmuch

...but it grew on me precisely because it provides a clue about how this
magic operates.