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

Grygorii Strashko
2016-05-23T15:07:16Z

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