IPod 6G Shutdown Hang -- Problem when Backlight on Hold is set to Off

[iPodVT]

I think that having Backlight on Hold set to Off is causing some flash-modded iPod Classics (ipod6g) to sometimes freeze when shutting down in response to Idle Poweroff timeouts and Sleep Timer timeouts, subsequently requiring a SELECT+MENU press-and-hold the next time I want to turn the device on.  The reasons I think the iPods are frozen and not entirely shutdown are: 1) I can't turn on the device with any 'normal' button presses nor by disengaging the Hold Switch nor by connecting to power, and 2) when I do restart the device via SELECT+MENU press-and-hold, the battery charge is significantly lower than I expect it to be (even accounting for the usual somewhat flaky fluctuating battery charge indications that are sometimes displayed with iPod Classics).

This problem does not occur when Backlight on Hold is set to Normal (I haven't tried setting it to On).  I first started experiencing the problem about a month or so ago (IIRC).  Around the same time, as part of a general attempt to try to conserve battery power, I changed the Backlight on Hold setting from Normal to Off and started pretty much always engaging the Hold switch when I wasn't actively controlling the iPod.  But it took some weeks before it occurred to me that there might be an association between that setting change and the freezes.  Now, after much observation and trying different scenarios I am able to deliberately and consistently make it happen on a few flash modded Classics - it never seems to happen with a Classic that has an HDD.  Below are the steps I take to make the problem occur.

USING IDLE TIMEOUT:
1 - Set Backlight on Hold to Off.
2 - Set Idle Poweroff to the briefest setting available.
3 - Start the iPod playing.
4 - Advance Now Playing to the last track in the current playlist.
5 - Advance the track to shortly before its end, leaving enough time to complete the following steps.
6 - Go to the WPS.
7 - Engage the Hold Switch.
8 - Wait until well after the iPod should have shutdown*, and then try to restart the iPod.

USING SLEEP TIMER TIMEOUT:
1 - Set Backlight on Hold to Off.
2 - Set the Sleep Timer Default to the briefest setting available and then start the Sleep Timer counting down.
3 - Start the iPod playing a playlist that is longer than the Sleep Timer countdown.
4 - Go to the WPS.
5 - Engage the Hold Switch.
6 - Wait until well after the iPod should have shutdown*, and then try to restart the iPod.

*It's hard/impossible to observe when the shutdown occurs because the LCD stays black and "Shutting down…" is not displayed.  Perhaps that is connected to the cause of the problem?  [Edit:  I know that in this situation the screen is supposed to stay black.]

All of the Classics I tested were running versions of Rockbox that had been posted within the last five days.

I had not encountered the problem with a 5th Gen iPod (ipodvideo) but I tested the same steps as above to verify.  I have not used any other iPod models in a while.

[iPodVT]

I thought that the iPods had to have been playing in order for the problem to occur, but just now I tried the Idle Timeout scenario without having the iPod play at all and got the freeze.  I don't know if it will consistently occur over multiple trials, so I'll check that and follow up.

[iPodVT]

More info:

Yes - those Classics that were freezing after Idle timeout do not require that the iPod had been in a Playing state for the freeze to occur.

I have again checked Idle timeout with Backlight on Hold set to Normal (instead of Off) and the Hold Switch engaged.  The iPod did not freeze, and I observed that at shutdown the LCD briefly lit up and displayed "Shutting down…".  As well, if Backlight on Hold is set to Off and I manually shutdown the iPod, the LCD displays "Shutting down…" because the Hold Switch is not engaged and the LCD is still lit.  I can't help but feel that Rockbox is not able to complete some event/action involved with displaying the shutting down msg and so it is seemingly suspended in a frozen 'on' state.

Also, when I wrote "…when I do restart the device via SELECT+MENU press-and-hold, the battery charge is significantly lower than I expect it to be" I should have specified that the restart attempt was some hours after the iPod should have shutdown.

[Bilgus]

sounds like a race
let me have a look

[Bilgus]

Does the setting Show Shutdown Message to no in startup shutdown settings fix the issue?

[iPodVT]

I just now set Show Shutdown Message to No and it still froze up and wouldn't restart normally.  So much for my theory...

[iPodVT]

In fact, with Show Shutdown Message set to NO the iPod freezes after Idle timeout regardless of whether or not the Lock Switch is engaged.

[Bilgus]

so  maybe something is waiting for the screen to be on

I was starting to dig into the backklight fade and sleep stuff so this is excellent

[iPodVT]

Cool.

[iPodVT]

Bilgus - I'm about to hit the hay for tonight unless you think there's a good chance that you would want me to assist in any way in the next 30 minutes or so. 

[Bilgus]

can you try this build https://www.mediafire.com/file/7qx7x9opw1bjs1n/ipod6G_rockbox_backlight_close.zip/file

it closes the backlight thread before shutdown

otherwise I need to sleep as well so I might have another build for you tomorrow

[iPodVT]

i'll let you know in a minute or two...

[Bilgus]

here is one more for a sanity check it sets backlight_on() on sshutdown

https://www.mediafire.com/file/0kj9to811ob1pih/iipod6G_rockbox_backlight_on.zip/file

[iPodVT]

can you try this build https://www.mediafire.com/file/7qx7x9opw1bjs1n/ipod6G_rockbox_backlight_close.zip/file

this one still freezes.  now i'll install and try the 2nd one.  standby...

[Bilgus]

it should turn on the backlight even with suppressing shutdown message if not I might have the wrong path