tokio::time::timeout not expiring precisely (Android)

[gladys88-88]

Hi all,

As mentioned in the title, I observe that the timeout is not expiring precisely in Android devices, understand that this might happen due to Android in sleep mode, and someone suggested wake-lock in this post (https://stackoverflow.com/questions/47472741/timer-not-expiring-precisely-during-sleep-state-in-android).

May I have any suggestion if tokio have similar stuff or how should I go about to overcome the "sleep" as I really need precise timer. TIA

[Darksonn]

When the device goes to sleep, a Tokio timer does not count any time that passed while it was asleep. You can read more about possibly changing that in #3185, but we are currently waiting for changes in std for that.

To get a timer that will properly count time that passes during sleep, you will need to use a timerfd hooked up to the CLOCK_BOOTTIME clock. You can hook the timerfd up to Tokio via an AsyncFd. There might already be a crate out there that does that for you, but a quick search yielded only outdated crates. You can find one implementation of this in Android's bluetooth driver here, but I don't think this implementation is published as a crate.

Be aware that even when using timerfd, the timer will not wake the device up. If the timer expires while the device is asleep, then it will fire immediately next time the device wakes up. I don't know how to actually wake up the device when a timer expires, unfortunately.

[gladys88-88]

Thanks for the reply. Appreciate it :)