Re: Kernel crash when syncing to usb-storage

[Rob Landley <rob@landley.net>]

On 11/18/20 4:09 AM, John Paul Adrian Glaubitz wrote:
> Hi Rob!
> 
> On 11/18/20 11:11 AM, Rob Landley wrote:
>>> Recently, I have started to see crashes when I try to sync a FAT filesystem
>>> on a USB pen drive. The crash is reproducible and seems to have been introduced
>>> in the 5.10 development cycle. I have not bisected the issue yet.
>>
>> Which board is this on? (Kernel config?)
> 
> SH-7785LCR, I'm attaching the kernel configuration for 5.9. I don't have the one
> for 5.10 at hand right now, but I used the same configuration for 5.9 and 5.10.
> 
>> Is it immediate or a ways into the backup?
> 
> It happens the moment the kernel tries to write the data to the USB drive.

Smells like an incorrectly initialized field in the interrupt state. Let's see...

# IRQ chip support
#
# end of IRQ chip support

# Interrupt controller options
#
CONFIG_INTC_USERIMASK=y
# CONFIG_INTC_MAPPING_DEBUG is not set
# end of SuperH / SH-Mobile Driver Options
# end of Kernel features

Very helpful.

CONFIG_IRQ_FORCED_THREADING=y
CONFIG_IRQ_WORK=y

I wonder what those do? I don't remember either...

> 5.9 is not affected, so it must be a regression with 5.10. I will bisect later
> this week.

There are many irq patches to choose from. And the DMA patches have potential
IRQ impact too (CONFIG_SH_DMA_IRQ_MULTI=y).

>> The stack trace says the idle tasks is handling an interrupt and crashing in the
>> interrupt controller code? Let's see...
>>
>> git log --no-merges v5.9..master arch/sh drivers/irqchip drivers/sh drivers/dma/sh
>>
>> This may not be a fat OR usb issue, there were some plumbing changes recently in
>> IRQ controllers and such, ala b388bdf2bac7 and f9ac7bbd6e45 and a7480c5d725c and
>> a00e85b581fd and 57733e009f0c and...
> 
> I will report back once I have found the culprit. I haven't had the time for bisecting
> yet.

Thanks.

I'm in Tokyo this month far _far_ away from my little blue board, and it's been
long enough since I've re-kerneled that I don't actually remember how anyway. (I
should poke you for a walkthrough over christmas...)

> Adrian
Rob