Re: [PATCH] PM / sleep: fix unbalanced pm runtime disable in __device_suspend_late()

[Grygorii Strashko <grygorii.strashko@ti.com>]

On 05/21/2016 12:26 AM, Rafael J. Wysocki wrote:
> On Friday, May 20, 2016 07:21:03 PM Grygorii Strashko wrote:
>> On 05/20/2016 03:18 PM, Rafael J. Wysocki wrote:
>>> On Thursday, May 19, 2016 08:11:34 PM Grygorii Strashko wrote:
>>>> On 05/19/2016 04:38 PM, Rafael J. Wysocki wrote:
>>>>> On Fri, May 13, 2016 at 8:03 PM, Grygorii Strashko
>>>>> <grygorii.strashko@ti.com> wrote:
>>>>>> The PM runtime will be left disabled for the device if its .suspend_late()
>>>>>> callback fails and async suspend is not allowed for this device. In
>>>>>> this case device will not be added in dpm_late_early_list and
>>>>>> dpm_resume_early() will ignore this device, as result PM runtime will
>>>>>> be disabled for it forever (side effect: after 8 subsequent failures
>>>>>> for the same device the PM runtime will be reenabled due to
>>>>>> disable_depth overflow).
>>>>>>
>>>>>> Hence, re-enable PM runtime in __device_suspend_late() if
>>>>>> .suspend_late() callback fails and async suspend is not allowed for
>>>>>> this device.
>>>>>>
>>>>>> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
>>>>>> ---
>>>>>>     drivers/base/power/main.c | 7 +++++--
>>>>>>     1 file changed, 5 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
>>>>>> index 6e7c3cc..9b266e5 100644
>>>>>> --- a/drivers/base/power/main.c
>>>>>> +++ b/drivers/base/power/main.c
>>>>>> @@ -1207,10 +1207,13 @@ static int __device_suspend_late(struct device *dev, pm_message_t state, bool as
>>>>>>            }
>>>>>>
>>>>>>            error = dpm_run_callback(callback, dev, state, info);
>>>>>> -       if (!error)
>>>>>> +       if (!error) {
>>>>>>                    dev->power.is_late_suspended = true;
>>>>>> -       else
>>>>>> +       } else {
>>>> 		Point [1]
>>>>>>                    async_error = error;
>>>>>> +               if (!is_async(dev))
>>>>>
>>>>> Why is the is_async() check necessary here?
>>>> 			
>>>> A: deviceX is suspended *async* and reached point [1], in this case:
>>>> - deviceX has been added in dpm_late_early_list already
>>>> - dpm_suspend_late() will detect async_error and call dpm_resume_early()
>>>> - dpm_resume_early() will call device_resume_early() for deviceX
>>>> - device_resume_early() will re-enable PM runtime
>>>> {
>>>> ...
>>>> 	if (!dev->power.is_late_suspended)
>>>> 		goto Out;
>>>>
>>>> 	...
>>>>    Out:
>>>> 	TRACE_RESUME(error);
>>>>
>>>> 	pm_runtime_enable(dev);
>>>> ^^^^^^^^^^^^
>>>> 	complete_all(&dev->power.completion);
>>>> 	return error;
>>>> }	
>>>> 	
>>>>
>>>> B: deviceX is suspended *sync* and reached point [1], in this case:
>>>> - deviceX has not been added in dpm_late_early_list yet
>>>> - dpm_suspend_late() will detect sync_error and call dpm_resume_early()
>>>> - dpm_resume_early() will ignore deviceX
>>>>
>>>> if i'll not check for !is_async(dev) then pm_runtime_enable(dev)
>>>> will be called twice for deviceX with this patch.
>>>
>>> OK, thanks!
>>>
>>> So to me, the problem is that we handle failures in that code inconsistently
>>> depending on whether or not async suspend/resume is enabled for the device.
>>>
>>> I'd rather make it consistent than add extra checks to it, so the patch below
>>> is how I would fix this.
>>>
>>> ---
>>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>> Subject: [PATCH] PM / sleep: Handle failures in device_suspend_late() consistently
>>>
>>> Grygorii Strashko reports:
>>>
>>>    The PM runtime will be left disabled for the device if its
>>>    .suspend_late() callback fails and async suspend is not allowed
>>>    for this device. In this case device will not be added in
>>>    dpm_late_early_list and dpm_resume_early() will ignore this
>>>    device, as result PM runtime will be disabled for it forever
>>>    (side effect: after 8 subsequent failures for the same device
>>>    the PM runtime will be reenabled due to disable_depth overflow).
>>>
>>> To fix this problem, add devices to dpm_late_early_list regardless
>>> of whether or not device_suspend_late() returns errors for them.
>>>
>>> That will ensure failures in there to be handled consistently for
>>> all devices regardless of their async suspend/resume status.
>>>
>>> Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>> ---
>>>    drivers/base/power/main.c |    5 +++--
>>>    1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> Index: linux-pm/drivers/base/power/main.c
>>> ===================================================================
>>> --- linux-pm.orig/drivers/base/power/main.c
>>> +++ linux-pm/drivers/base/power/main.c
>>> @@ -1267,14 +1267,15 @@ int dpm_suspend_late(pm_message_t state)
>>>    		error = device_suspend_late(dev);
>>>
>>>    		mutex_lock(&dpm_list_mtx);
>>> +		if (!list_empty(&dev->power.entry))
>>> +			list_move(&dev->power.entry, &dpm_late_early_list);
>>> +
>>>    		if (error) {
>>>    			pm_dev_err(dev, state, " late", error);
>>>    			dpm_save_failed_dev(dev_name(dev));
>>>    			put_device(dev);
>>>    			break;
>>>    		}
>>> -		if (!list_empty(&dev->power.entry))
>>> -			list_move(&dev->power.entry, &dpm_late_early_list);
>>>    		put_device(dev);
>>>
>>>    		if (async_error)
>>>
>>
>> Yep, it works too.
>> Tested-by: Grygorii Strashko <grygorii.strashko@ti.com>
>
> OK, thanks!
>
> Applied.
>

Thanks.


-- 
regards,
-grygorii