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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20251113113529.vnfvc6cqmk2ct4kl@lcpd911>
Date: Thu, 13 Nov 2025 17:05:29 +0530
From: Dhruva Gole <d-gole@...com>
To: <dan.j.williams@...el.com>
CC: "Rafael J. Wysocki" <rafael@...nel.org>, Jonathan Cameron
	<jonathan.cameron@...wei.com>, Frank Li <Frank.Li@....com>, 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>, 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

On Nov 12, 2025 at 13:27:17 -0800, dan.j.williams@...el.com wrote:
> 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.

Yeah you're right, I agree. Having users explicitly pass on the '&' provides much
more clarity on what's going on than hiding it internally.

-- 
Best regards,
Dhruva Gole
Texas Instruments Incorporated