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

Doug Anderson dianders at chromium.org
Thu Nov 8 06:26:56 AEDT 2018


On Wed, Nov 7, 2018 at 10:23 AM Andy Shevchenko
<andriy.shevchenko at linux.intel.com> wrote:
> 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.

Can you be more specific, please?  Which section of the "MAINTAINERS"
file should I be looking at for the "console" you are thinking of?
Certainly there are lots of hits for "console" in MAINTAINERS but I
don't think I see any that are relevant that I missed.  Grepping:

$ grep  -i console MAINTAINERS
F:      drivers/video/console/sti*
F:      drivers/char/virtio_console.c
F:      include/linux/virtio_console.h
F:      include/uapi/linux/virtio_console.h

...none of those seem relevant upon first glance but I'm happy to
stand corrected.

Ah!  Based on who you added to the CC list I guess you meant to CC
"printk" folks?

M:      Petr Mladek <pmladek at suse.com>
M:      Sergey Senozhatsky <sergey.senozhatsky at gmail.com>
R:      Steven Rostedt <rostedt at goodmis.org>
S:      Maintained
F:      kernel/printk/
F:      include/linux/printk.h

I'd be happy to CC those folks on future spins (if there are any).
I'm not convinced that these patches are directly relevant to the
printk subsystem, but I'm always happy for more people to have a
chance to review patches.

Hopefully anyone who needs this patch can find it on one of the
relevant mailing lists.  I screwed up and missed LKML this time
around, but there are plenty of other mailing lists here that it could
be found on.  If requested I'm also happy to re-post the same series
adding those 3 people if that's what everyone wants.


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