linux-kernel - Re: [PATCH v1] PM: sleep: core: Synchronize runtime PM status of parents and children

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

Message-ID: <Z6Y0NlW40yHTIlzm@hovoldconsulting.com>
Date: Fri, 7 Feb 2025 17:26:30 +0100
From: Johan Hovold <johan@...nel.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Jon Hunter <jonathanh@...dia.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux PM <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Bjorn Helgaas <helgaas@...nel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Kevin Xie <kevin.xie@...rfivetech.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v1] PM: sleep: core: Synchronize runtime PM status of
 parents and children

On Fri, Feb 07, 2025 at 05:06:32PM +0100, Johan Hovold wrote:
> On Fri, Feb 07, 2025 at 04:41:18PM +0100, Rafael J. Wysocki wrote:
> > On Fri, Feb 7, 2025 at 3:45 PM Johan Hovold <johan@...nel.org> wrote:
> > > On Fri, Feb 07, 2025 at 02:50:29PM +0100, Johan Hovold wrote:
> 
> > > Ok, so the driver data is never set and runtime PM is never enabled for
> > > this simple bus device, which uses pm_runtime_force_suspend() for system
> > > sleep.
> > 
> > This is kind of confusing.  Why use pm_runtime_force_suspend() if
> > runtime PM is never enabled and cannot really work?
> 
> It's only done for some buses that this driver handles. The driver is
> buggy; I'm preparing a fix for it regardless of the correctness of the
> commit that now triggered this.

Hmm. The driver implementation is highly odd, but actually works as long
as the runtime PM status is left at 'suspended' (as
pm_runtime_force_resume() won't enable runtime PM unless it was enabled
before suspend).

So we'd strictly only need something like the below if we are going to
keep the set_active propagation.

Johan


diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c
index 5dea31769f9a..d8e029e7e53f 100644
--- a/drivers/bus/simple-pm-bus.c
+++ b/drivers/bus/simple-pm-bus.c
@@ -109,9 +109,29 @@ static int simple_pm_bus_runtime_resume(struct device *dev)
 	return 0;
 }
 
+static int simple_pm_bus_suspend(struct device *dev)
+{
+	struct simple_pm_bus *bus = dev_get_drvdata(dev);
+
+	if (!bus)
+		return 0;
+
+	return pm_runtime_force_suspend(dev);
+}
+
+static int simple_pm_bus_resume(struct device *dev)
+{
+	struct simple_pm_bus *bus = dev_get_drvdata(dev);
+
+	if (!bus)
+		return 0;
+
+	return pm_runtime_force_resume(dev);
+}
+
 static const struct dev_pm_ops simple_pm_bus_pm_ops = {
 	RUNTIME_PM_OPS(simple_pm_bus_runtime_suspend, simple_pm_bus_runtime_resume, NULL)
-	NOIRQ_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
+	NOIRQ_SYSTEM_SLEEP_PM_OPS(simple_pm_bus_suspend, simple_pm_bus_resume)
 };
 
 #define ONLY_BUS	((void *) 1) /* Match if the device is only a bus. */