Re: [PATCH v2 0/5] serial: Finish sysrq on qcom_geni; fix sysrq vs. lockdep on 8250

Andy Shevchenko
2018-11-07T18:23:49Z

On Tue, Oct 30, 2018 at 03:11:02PM -0700, Douglas Anderson wrote:
> I started out this series trying to make sysrq work over the serial
> console on qcom_geni_serial, then fell into a rat's nest.
>
> To solve the deadlock I faced when enabling sysrq I tried to borrow
> code from '8250_port.c' which avoided grabbing the port lock in
> console_write(). ...but since these days I try to run with lockdep on
> all the time, I found it caused an annoying lockdep splat (which I
> also reproduced on my rk3399 board). ...so I instead changed my
> qcom_geni_serial solution to borrow code from 'msm_serial.c'
>
> I wasn't super happy with the solution in 'msm_serial.c' though. I
> don't like releasing the spinlock there. Not only is it ugly but it
> means we are unlocking / re-locking _all the time_ even though sysrq
> characters are rare. ...so I came up with what I think is a better
> solution and then implemented it for qcom_geni_serial.
>
> Since I had a good way to test 8250-based UARTs, I also fixed that
> driver to use my new method. When doing so, I ran into a missing
> include in serial_core.h. NOTE: I didn't have a way to test
> msm_serial.c at all, so I didn't switch that (or all other serial
> drivers for that matter) to the new method.
>
> NOTE: from a serial point of view v2 is the same as v1 but I've
> removed the extra kgdb-related patches and made it obvious that this
> is really for all sysrq, not just kgdb. I've also generally tried to
> curate the CCs more properly.

It seems your forgot console people to Cc.

>
>
> Douglas Anderson (5):
> serial: qcom_geni_serial: Finish supporting sysrq
> serial: core: Allow processing sysrq at port unlock time
> serial: qcom_geni_serial: Process sysrq at port unlock time
> serial: core: Include console.h from serial_core.h
> serial: 8250: Process sysrq at port unlock time
>
> drivers/tty/serial/8250/8250_aspeed_vuart.c | 6 +++-
> drivers/tty/serial/8250/8250_fsl.c | 6 +++-
> drivers/tty/serial/8250/8250_omap.c | 6 +++-
> drivers/tty/serial/8250/8250_port.c | 8 ++---
> drivers/tty/serial/qcom_geni_serial.c | 10 ++++--
> include/linux/serial_core.h | 38 ++++++++++++++++++++-
> 6 files changed, 63 insertions(+), 11 deletions(-)
>
> --
> 2.19.1.568.g152ad8e336-goog
>

--
With Best Regards,
Andy Shevchenko