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

Douglas Anderson
2018-10-30T22:11:02Z

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.

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(-)

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2.19.1.568.g152ad8e336-goog