Re: Hot-plugging microSD on Raspberry Pi under FreeBSD

On 2021-Dec-26, at 14:47, bob prohaska <[email protected]> wrote:

> On Sun, Dec 26, 2021 at 01:00:38PM -0800, Mark Millard via freebsd-arm wrote:
>> On 2021-Dec-26, at 11:23, bob prohaska <[email protected]> wrote:
>> 
>>> 
>>> Obviously filesystems have to be gracefully unmounted, but is
>>> that all? Can the kernel be "aware" of an unused device and
>>> get confused if it goes away?
>> 
>> As I remember, for FreeBSD,
>> 
>> A) The built-in microsd card slot works fine for swapping
>>   media that are not mounted at the time.
> 
> Ok, that's reassuring. I observed corruption of microSD card FAT 
> partitionss and wondered if hot-plugging might be the cause.

I could do a similar check of this context later.

>> 
>> but, for example (no mounts involved, RPi4B 8GiByte test context),
>> 
>> B.0) Plug-in the USB reader, no media present. (USB3 example here.)
>> B.1) Insert a 128 GiByte media to the reader.
>> B.2) Remove that media.
>> B.3) Insert a 32 GiByte media to the reader
>>     (same slot in the reader).
>> 
>> Result:
>> 
>> (da4:umass-sim1:1:0:3): READ(10). CDB: 28 00 0e e2 af ff 00 00 01 00 
> 
> [...disk errors snipped....]
> 
> Was the Pi4 running from a USB hard disk?

USB3 SSD. I do not have the marginal/insufficient
power issues that you have.

> I ask because plugging in a USB reader to my RasPiOS Pi4 while booted 
> from a USB hard disk seems to disrupt communication with the boot drive. 

You have described having a marginal/insufficient
power context in other messages.

> It doesn't crash immediately but can't be gracefully rebooted.
> 
>> If you do the 32 GiByte first instead, then for the 128 GiByte you
>> get notices from GEOM_PART about "was automatically resized"
>> but it does not "address out of range".
> 
> That seems like the "confusion" I was wondering about. The kernel
> notices the first card insertion, fails to notice the removal and
> then mis-attributes the change to a partition resize.

I disconnect the reader, swap media, and reconnect. That
handles things fine.

>> I expect that swapping two media of the same capacity would
>> be less likely to generate any messages, but that does not
>> mean that such a swap would be handled fully correctly.
>> 
>> So I unplug the whole reader to swap media. This is messier
>> if multiple slots are in use (more unmounts and later
>> remounts).
> 
> That chain of events crashes my RasPiOS Pi4, at least when it's also
> booted from a USB drive. 
> 

You have described having a marginal/insufficient
power context in other messages.




===
Mark Millard
marklmi at yahoo.com