Commit c1567f81 authored Feb 12, 2019 by Rafael J. Wysocki Committed by Greg Kroah-Hartman Feb 13, 2019

PM-runtime: Fix __pm_runtime_set_status() race with runtime resume



Commit 4080ab08 ("PM-runtime: Take suppliers into account in
__pm_runtime_set_status()") introduced a race condition that may
trigger if __pm_runtime_set_status() is used incorrectly (that is,
if it is called when PM-runtime is enabled for the target device
and working).

In that case, if the original PM-runtime status of the device is
RPM_SUSPENDED, a runtime resume of the device may occur after
__pm_runtime_set_status() has dropped its power.lock spinlock
and before deactivating its suppliers, so the suppliers may be
deactivated while the device is PM-runtime-active which may lead
to functional issues.

To avoid that, modify __pm_runtime_set_status() to check whether
or not PM-runtime is enabled for the device before activating its
suppliers (if the new status is RPM_ACTIVE) and either return an
error if that's the case or increment the device's disable_depth
counter to prevent PM-runtime from being enabled for it while
the remaining part of the function is running (disable_depth is
then decremented on the way out).

Fixes: 4080ab08 ("PM-runtime: Take suppliers into account in __pm_runtime_set_status()")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent daaef255

drivers/base/power/runtime.c

+18 −6

Original line number	Diff line number	Diff line
		@@ -1106,6 +1106,22 @@ int __pm_runtime_set_status(struct device *dev, unsigned int status)
		if (status != RPM_ACTIVE && status != RPM_SUSPENDED)
		return -EINVAL;

		spin_lock_irq(&dev->power.lock);

		/*
		* Prevent PM-runtime from being enabled for the device or return an
		* error if it is enabled already and working.
		*/
		if (dev->power.runtime_error \|\| dev->power.disable_depth)
		dev->power.disable_depth++;
		else
		error = -EAGAIN;

		spin_unlock_irq(&dev->power.lock);

		if (error)
		return error;

		/*
		* If the new status is RPM_ACTIVE, the suppliers can be activated
		* upfront regardless of the current status, because next time
		@@ -1124,12 +1140,6 @@ int __pm_runtime_set_status(struct device *dev, unsigned int status)

		spin_lock_irq(&dev->power.lock);

		if (!dev->power.runtime_error && !dev->power.disable_depth) {
		status = dev->power.runtime_status;
		error = -EAGAIN;
		goto out;
		}

		if (dev->power.runtime_status == status \|\| !parent)
		goto out_set;

		@@ -1182,6 +1192,8 @@ int __pm_runtime_set_status(struct device *dev, unsigned int status)
		device_links_read_unlock(idx);
		}

		pm_runtime_enable(dev);

		return error;
		}
		EXPORT_SYMBOL_GPL(__pm_runtime_set_status);

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