Commit 098dff73 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

PM: Fix potential issue with failing asynchronous suspend 



There is a potential issue with the asynchronous suspend code that
a device driver suspending asynchronously may not notice that it
should back off.  There are two failing scenarions, (1) when the
driver is waiting for a driver suspending synchronously to complete
and that second driver returns error code, in which case async_error
won't be set and the waiting driver will continue suspending and (2)
after the driver has called device_pm_wait_for_dev() and the waited
for driver returns error code, in which case the caller of
device_pm_wait_for_dev() will not know that there was an error and
will continue suspending.

To fix this issue make __device_suspend() set async_error, so
async_suspend() doesn't need to set it any more, and make
device_pm_wait_for_dev() return async_error, so that its callers
can check whether or not they should continue suspending.

No more changes are necessary, since device_pm_wait_for_dev() is
not used by any drivers' suspend routines.

Reported-by: default avatarColin Cross <ccross@android.com>
Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
Acked-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 074037ec

drivers/base/power/main.c

+9 −6
Original line number Diff line number Diff line
@@ -51,6 +51,8 @@ static pm_message_t pm_transition; 
 */

static bool transition_started;



static int async_error;



/**

 * device_pm_init - Initialize the PM-related part of a device object.

 * @dev: Device object being initialized.
@@ -602,6 +604,7 @@ static void dpm_resume(pm_message_t state) 
	INIT_LIST_HEAD(&list);

	mutex_lock(&dpm_list_mtx);

	pm_transition = state;

	async_error = 0;



	list_for_each_entry(dev, &dpm_list, power.entry) {

		if (dev->power.status < DPM_OFF)
@@ -831,8 +834,6 @@ static int legacy_suspend(struct device *dev, pm_message_t state, 
	return error;

}



static int async_error;



/**

 * device_suspend - Execute "suspend" callbacks for given device.

 * @dev: Device to handle.
@@ -887,6 +888,9 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async) 
	device_unlock(dev);

	complete_all(&dev->power.completion);



	if (error)

		async_error = error;



	return error;

}
@@ -896,10 +900,8 @@ static void async_suspend(void *data, async_cookie_t cookie) 
	int error;



	error = __device_suspend(dev, pm_transition, true);

	if (error) {

	if (error)

		pm_dev_err(dev, pm_transition, " async", error);

		async_error = error;

	}



	put_device(dev);

}
@@ -1087,8 +1089,9 @@ EXPORT_SYMBOL_GPL(__suspend_report_result); 
 * @dev: Device to wait for.

 * @subordinate: Device that needs to wait for @dev.

 */

void device_pm_wait_for_dev(struct device *subordinate, struct device *dev)

int device_pm_wait_for_dev(struct device *subordinate, struct device *dev)

{

	dpm_wait(dev, subordinate->power.async_suspend);

	return async_error;

}

EXPORT_SYMBOL_GPL(device_pm_wait_for_dev);

include/linux/pm.h

+5 −2
Original line number Diff line number Diff line
@@ -559,7 +559,7 @@ extern void __suspend_report_result(const char *function, void *fn, int ret); 
		__suspend_report_result(__func__, fn, ret);		\

	} while (0)



extern void device_pm_wait_for_dev(struct device *sub, struct device *dev);

extern int device_pm_wait_for_dev(struct device *sub, struct device *dev);

#else /* !CONFIG_PM_SLEEP */



#define device_pm_lock() do {} while (0)
@@ -572,7 +572,10 @@ static inline int dpm_suspend_start(pm_message_t state) 


#define suspend_report_result(fn, ret)		do {} while (0)



static inline void device_pm_wait_for_dev(struct device *a, struct device *b) {}

static inline int device_pm_wait_for_dev(struct device *a, struct device *b)

{

	return 0;

}

#endif /* !CONFIG_PM_SLEEP */



/* How to reorder dpm_list after device_move() */

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