linux-kernel - [PATCH v3 5/9] PM: Check power.needs_force_resume in pm_runtime_force

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 for Android: free password hash cracker in your pocket

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

Message-ID: <1855933.VLH7GnMWUR@rjwysocki.net>
Date: Fri, 27 Jun 2025 21:19:31 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Linux ACPI <linux-acpi@...r.kernel.org>,
 Linux PCI <linux-pci@...r.kernel.org>, Ulf Hansson <ulf.hansson@...aro.org>,
 Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject:
 [PATCH v3 5/9] PM: Check power.needs_force_resume in
 pm_runtime_force_suspend()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Add a power.needs_force_resume check to pm_runtime_force_suspend() so
it need not rely on the runtime PM status of the device when deciding
whether or not to return early.

With the new check in place, pm_runtime_force_suspend() will also skip
devices with the runtime PM status equal to RPM_ACTIVE if they have
power.needs_force_resume set, so it won't need to change the RPM
status of the device to RPM_SUSPENDED in addition to setting
power.needs_force_resume in the case when pm_runtime_need_not_resume()
return false.

That allows the runtime PM status update to be removed from
pm_runtime_force_resume(), so the runtime PM status remains unchanged
between the pm_runtime_force_suspend() and pm_runtime_force_resume()
calls.

This change potentially unbreaks drivers that call pm_runtime_force_suspend()
from their ->remove() callbacks because currently, if the device being
unbound from its driver has a parent with enabled runtime PM and/or
(possibly) device links respecting runtime PM to suppliers, and it is
RPM_ACTIVE when the remove takes place, pm_runtime_force_suspend() will
not drop the parent's child count and the suppliers' runtime PM usage
counters after force-suspending the device unless pm_runtime_need_not_resume()
returns 'true' for it.  Moreover, because pm_runtime_force_suspend()
changes the device's runtime PM status to RPM_SUSPENDED, in the above
case pm_runtime_reinit() will not cause those counters to drop, so they
will remain nonzero forever effectively preventing the devices in
question from runtime-suspending going forward.

This change is also needed for pm_runtime_force_suspend() to work
with PCI PM and ACPI PM after subsequent changes.  Namely, say
DPM_FLAG_SMART_SUSPEND is set for a PCI device and its driver uses
pm_runtime_force_suspend() as its ->suspend() callback.  If
pm_runtime_force_suspend() changed the runtime PM status of the
device to RPM_SUSPENDED, pci_pm_suspend_noirq() would skip the
device due to the dev_pm_skip_suspend() check.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---

v2 -> v3:
   * Update changelog (explanation why it potentially unbreaks some drivers and
     why the subsequent changes depend on it).
   * Reorder (it was [4/9] previously).

v1 -> v2: Corresponds to patch [2/9] (that was posted as [0/9] by mistake) in v1.

---
 drivers/base/power/runtime.c |   21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1969,7 +1969,7 @@
 	int ret;

 	pm_runtime_disable(dev);
-	if (pm_runtime_status_suspended(dev))
+	if (pm_runtime_status_suspended(dev) || dev->power.needs_force_resume)
 		return 0;

 	callback = RPM_GET_CALLBACK(dev, runtime_suspend);
@@ -1984,15 +1984,16 @@
 	/*
 	 * If the device can stay in suspend after the system-wide transition
 	 * to the working state that will follow, drop the children counter of
-	 * its parent, but set its status to RPM_SUSPENDED anyway in case this
-	 * function will be called again for it in the meantime.
+	 * its parent and the usage counters of its suppliers.  Otherwise, set
+	 * power.needs_force_resume to let pm_runtime_force_resume() know that
+	 * the device needs to be taken care of and to prevent this function
+	 * from handling the device again in case the device is passed to it
+	 * once more subsequently.
 	 */
-	if (pm_runtime_need_not_resume(dev)) {
+	if (pm_runtime_need_not_resume(dev))
 		pm_runtime_set_suspended(dev);
-	} else {
-		__update_runtime_status(dev, RPM_SUSPENDED);
+	else
 		dev->power.needs_force_resume = true;
-	}

 	return 0;

@@ -2033,12 +2034,6 @@
 	    pm_runtime_status_suspended(dev)))
 		goto out;

-	/*
-	 * The value of the parent's children counter is correct already, so
-	 * just update the status of the device.
-	 */
-	__update_runtime_status(dev, RPM_ACTIVE);
-
 	callback = RPM_GET_CALLBACK(dev, runtime_resume);

 	dev_pm_disable_wake_irq_check(dev, false);