linux-kernel - Re: [PATCH v1 1/3] PM: runtime: Introduce PM_RUNTIME_ACQUIRE_OR

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Message-ID: <20251016133854.00003669@huawei.com>
Date: Thu, 16 Oct 2025 13:38:54 +0100
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
CC: Linux PM <linux-pm@...r.kernel.org>, Takashi Iwai <tiwai@...e.de>, LKML
	<linux-kernel@...r.kernel.org>, Linux PCI <linux-pci@...r.kernel.org>, "Alex
 Williamson" <alex.williamson@...hat.com>, Bjorn Helgaas <helgaas@...nel.org>,
	Zhang Qilong <zhangqilong3@...wei.com>, Ulf Hansson <ulf.hansson@...aro.org>,
	Frank Li <Frank.Li@....com>, Dhruva Gole <d-gole@...com>, Mika Westerberg
	<mika.westerberg@...ux.intel.com>, "Linux ACPI" <linux-acpi@...r.kernel.org>,
	Dan Williams <dan.j.williams@...el.com>, David Lechner
	<dlechner@...libre.com>, "Fabio M. De Francesco"
	<fabio.maria.de.francesco@...ux.intel.com>
Subject: Re: [PATCH v1 1/3] PM: runtime: Introduce
 PM_RUNTIME_ACQUIRE_OR_FAIL() macro

On Wed, 15 Oct 2025 16:02:02 +0200
"Rafael J. Wysocki" <rafael@...nel.org> wrote:

> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> There appears to be an emerging pattern in which guard
> pm_runtime_active_try is used for resuming the given device and
> incrementing its runtime PM usage counter if the resume has been
> successful, that is followed by an ACQUIRE_ERR() check on the guard
> variable and if that triggers, a specific error code is returned, for
> example:
> 
> 	ACQUIRE(pm_runtime_active_try, pm)(dev);
> 	if (ACQUIRE_ERR(pm_runtime_active_try, &pm))
> 		return -ENXIO
> 
> Introduce a macro called PM_RUNTIME_ACQUIRE_OR_FAIL() representing the
> above sequence of statements that can be used to avoid code duplication
> wherever that sequence would be used.
> 
> Use this macro right away in the PCI sysfs code where the above pattern
> is already present.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> Admittedly, the new macro is slightly on the edge, but it really helps
> reduce code duplication, so here it goes.

Fully agree with the 'on the edge'. 

This looks somewhat like the some of the earlier attempts to come up with
a general solution before ACQUIRE().  Linus was fairly clear on his opinion of
a proposal that looked a bit similar to this
cond_guard(mutex_intr, return -EINTR, &mutex);

https://lore.kernel.org/all/CAHk-=win7bwWhPJ=iuW4h-sDTqbX6v9_LJnMaO3KxVfPSs81bQ@mail.gmail.com/

+CC a few people who might have better memories of where things went than I do.

The solution you have here has the benefit of clarity that all it can do is
return the error code.

Thanks,

Jonathan


> 
> Any feedback (good, bad, ugly) will be appreciated.
> 
> Thanks!
> 
> ---
>  drivers/pci/pci-sysfs.c    |    4 +---
>  include/linux/pm_runtime.h |    5 +++++
>  2 files changed, 6 insertions(+), 3 deletions(-)
> 
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -1517,9 +1517,7 @@ static ssize_t reset_method_store(struct
>  		return count;
>  	}
>  
> -	ACQUIRE(pm_runtime_active_try, pm)(dev);
> -	if (ACQUIRE_ERR(pm_runtime_active_try, &pm))
> -		return -ENXIO;
> +	PM_RUNTIME_ACQUIRE_OR_FAIL(dev, -ENXIO);
>  
>  	if (sysfs_streq(buf, "default")) {
>  		pci_init_reset_methods(pdev);
> --- a/include/linux/pm_runtime.h
> +++ b/include/linux/pm_runtime.h
> @@ -637,6 +637,11 @@ DEFINE_GUARD_COND(pm_runtime_active_auto
>  DEFINE_GUARD_COND(pm_runtime_active_auto, _try_enabled,
>  		  pm_runtime_resume_and_get(_T))
>  
> +#define PM_RUNTIME_ACQUIRE_OR_FAIL(dev, error)		\
> +	ACQUIRE(pm_runtime_active_try, __pm)(dev);	\
> +	if (ACQUIRE_ERR(pm_runtime_active_try, &__pm))	\
> +		return error
> +
>  /**
>   * pm_runtime_put_sync - Drop device usage counter and run "idle check" if 0.
>   * @dev: Target device.
> 
> 
>