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

Grygorii Strashko
2016-05-19T17:11:51Z

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.

>
>> + pm_runtime_enable(dev);
>> + }
>>
>> Complete:
>> TRACE_SUSPEND(error);
>> --

--
regards,
-grygorii