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

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Message-ID: <5068916.31r3eYUQgx@rafael.j.wysocki>
Date: Wed, 12 Nov 2025 20:44:06 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: 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

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?

---
From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Subject: [PATCH v2] PM: runtime: Wrapper macros for ACQUIRE()/ACQUIRE_ERR()

Add several wrapper macros for ACQUIRE()/ACQUIRE_ERR() and runtime PM
usage counter guards introduced recently: pm_runtime_active_try,
pm_runtime_active_auto_try, pm_runtime_active_try_enabled, and
pm_runtime_active_auto_try_enabled.

The new macros are simpler and should be more straightforward to use.

For example, they can be used for rewriting a piece of code like below:

        ACQUIRE(pm_runtime_active_try, pm)(dev);
        if ((ret = ACQUIRE_ERR(pm_runtime_active_try, &pm)))
                return ret;

in the following way:

        PM_RUNTIME_ACQUIRE(dev, pm);
        if ((ret = PM_RUNTIME_ACQUIRE_ERR(pm)))
                return ret;

If the original code does not care about the specific error code
returned when attempting to resume the device:

        ACQUIRE(pm_runtime_active_try, pm)(dev);
        if (ACQUIRE_ERR(pm_runtime_active_try, &pm))
                return -ENXIO;

it may be changed like this:

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

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 include/linux/pm_runtime.h |   25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

--- a/include/linux/pm_runtime.h
+++ b/include/linux/pm_runtime.h
@@ -637,6 +637,31 @@ DEFINE_GUARD_COND(pm_runtime_active_auto
 DEFINE_GUARD_COND(pm_runtime_active_auto, _try_enabled,
 		  pm_runtime_resume_and_get(_T), _RET == 0)

+/* ACQUIRE() wrapper macros for the guards defined above. */
+
+#define PM_RUNTIME_ACQUIRE(dev, var_name)	\
+	ACQUIRE(pm_runtime_active_try, var_name)(dev)
+
+#define PM_RUNTIME_ACQUIRE_AUTOSUSPEND(dev, var_name)	\
+	ACQUIRE(pm_runtime_active_auto_try, var_name)(dev)
+
+#define PM_RUNTIME_ACQUIRE_IF_ENABLED(dev, var_name)	\
+	ACQUIRE(pm_runtime_active_try_enabled, var_name)(dev)
+
+#define PM_RUNTIME_ACQUIRE_IF_ENABLED_AUTOSUSPEND(dev, var_name)	\
+	ACQUIRE(pm_runtime_active_auto_try_enabled, var_name)(dev)
+
+/*
+ * ACQUIRE_ERR() wrapper macro for guard pm_runtime_active.
+ *
+ * Always check PM_RUNTIME_ACQUIRE_ERR() after using one of the
+ * PM_RUNTIME_ACQUIRE*() macros defined above (yes, it can be used
+ * with any of them) and avoid accessing the given device if it is
+ * nonzero.
+ */
+#define PM_RUNTIME_ACQUIRE_ERR(var_name)	\
+	ACQUIRE_ERR(pm_runtime_active, &var_name)
+
 /**
  * pm_runtime_put_sync - Drop device usage counter and run "idle check" if 0.
  * @dev: Target device.