Re: [PATCH v2 2/7] serial: qcom-geni: fix shutdown race

[Doug Anderson]

Hi,

On Tue, Oct 1, 2024 at 5:51 AM Johan Hovold <johan+linaro@xxxxxxxxxx> wrote:
>
> A commit adding back the stopping of tx on port shutdown failed to add
> back the locking which had also been removed by commit e83766334f96
> ("tty: serial: qcom_geni_serial: No need to stop tx/rx on UART
> shutdown").

Hmmm, when I look at that commit it makes me think that the problem
that commit e83766334f96 ("tty: serial: qcom_geni_serial: No need to
stop tx/rx on UART shutdown") was fixing was re-introduced by commit
d8aca2f96813 ("tty: serial: qcom-geni-serial: stop operations in
progress at shutdown"). ...and indeed, it was. :(

I can't interact with kgdb if I do this:

1. ssh over to DUT
2. Kill the console process (on ChromeOS stop console-ttyMSM0)
3. Drop in the debugger (echo g > /proc/sysrq-trigger)

This bug predates your series, but since it touches the same code
maybe you could fix it at the same time? I will note that commit
e83766334f96 ("tty: serial: qcom_geni_serial: No need to stop tx/rx on
UART shutdown") mentions that it wasn't required for FIFO mode--only
DMA...

Aside from the pre-existing bug, I agree that the locking should be there.


-Doug