Some wakeup event happens every frequently between reading
wakeup_count and writing back wakeup_count.
They changed wakeup event count so writes fail and usespace doesn't
continue to suspend. However, such
occurrences are not counted in ws->wakeup_count. I spent quite
sometime finding out the problematic wakeup
event with inaccurate wakeup_count : )
Thanks,
jin
On Fri, May 15, 2015 at 5:34 PM, Rafael J. Wysocki <r...@rjwysocki.net> wrote:
> On Wednesday, April 22, 2015 05:50:11 PM Jin Qian wrote:
>> user-space aborts suspend attempt if writing wakeup_count failed.
>> Count the write failure towards wakeup_count.
>
> A use case, please?
>
>> Signed-off-by: Jin Qian <jinq...@android.com>
>> ---
>> drivers/base/power/wakeup.c | 17 +++++++++++++++++
>> 1 file changed, 17 insertions(+)
>>
>> diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
>> index f24c622..bdb45f3 100644
>> --- a/drivers/base/power/wakeup.c
>> +++ b/drivers/base/power/wakeup.c
>> @@ -57,6 +57,8 @@ static LIST_HEAD(wakeup_sources);
>>
>> static DECLARE_WAIT_QUEUE_HEAD(wakeup_count_wait_queue);
>>
>> +static ktime_t last_read_time;
>> +
>> /**
>> * wakeup_source_prepare - Prepare a new wakeup source for initialization.
>> * @ws: Wakeup source to prepare.
>> @@ -771,10 +773,15 @@ void pm_wakeup_clear(void)
>> bool pm_get_wakeup_count(unsigned int *count, bool block)
>> {
>> unsigned int cnt, inpr;
>> + unsigned long flags;
>>
>> if (block) {
>> DEFINE_WAIT(wait);
>>
>> + spin_lock_irqsave(&events_lock, flags);
>> + last_read_time = ktime_get();
>> + spin_unlock_irqrestore(&events_lock, flags);
>> +
>> for (;;) {
>> prepare_to_wait(&wakeup_count_wait_queue, &wait,
>> TASK_INTERRUPTIBLE);
>> @@ -806,6 +813,7 @@ bool pm_save_wakeup_count(unsigned int count)
>> {
>> unsigned int cnt, inpr;
>> unsigned long flags;
>> + struct wakeup_source *ws;
>>
>> events_check_enabled = false;
>> spin_lock_irqsave(&events_lock, flags);
>> @@ -813,6 +821,15 @@ bool pm_save_wakeup_count(unsigned int count)
>> if (cnt == count && inpr == 0) {
>> saved_count = count;
>> events_check_enabled = true;
>> + } else {
>> + rcu_read_lock();
>> + list_for_each_entry_rcu(ws, &wakeup_sources, entry) {
>> + if (ws->active ||
>> + ktime_compare(ws->last_time, last_read_time) > 0) {
>> + ws->wakeup_count++;
>> + }
>> + }
>> + rcu_read_unlock();
>> }
>> spin_unlock_irqrestore(&events_lock, flags);
>> return events_check_enabled;
>>
>
> --
> I speak only for myself.
> Rafael J. Wysocki, Intel Open Source Technology Center.
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