From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Date: Tue, 30 Oct 2018 12:36:27 +0000 Subject: Re: [PATCH 0/7] serial: Finish kgdb on qcom_geni; fix many lockdep splats w/ kgdb Message-Id: <20181030123627.GS10650@smile.fi.intel.com> List-Id: References: <20181029180707.207546-1-dianders@chromium.org> In-Reply-To: <20181029180707.207546-1-dianders@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Douglas Anderson Cc: Jason Wessel , Daniel Thompson , tglx@linutronix.de, mingo@kernel.org, gregkh@linuxfoundation.org, linux-arm-msm@vger.kernel.org, kgdb-bugreport@lists.sourceforge.net, nm@ti.com, linux-mips@linux-mips.org, dalias@libc.org, catalin.marinas@arm.com, vigneshr@ti.com, linux-aspeed@lists.ozlabs.org, linux-sh@vger.kernel.org, peterz@infradead.org, will.deacon@arm.com, mhocko@suse.com, paulus@samba.org, hpa@zytor.com, sparclinux@vger.kernel.org, marex@denx.de, sfr@canb.auug.org.au, ysato@users.sourceforge.jp, linux-hexagon@vger.kernel.org, x86@kernel.org, linux@armlinux.org.uk, pombredanne@nexb.com, tony@atomide.com, mingo@redhat.com, joel@jms.id.au, linux-serial@vger.kernel.org, rolf.evers.fischer@aptiv.com, jhogan@kernel.or On Mon, Oct 29, 2018 at 11:07:00AM -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 > msm_serial.c at all, so I didn't switch that (or all other serial > drivers for that matter) to the new method. > > After fixing all the above issues, I found the next lockdep splat in > kgdb and I think I've worked around it in a good-enough way, but I'm > much less confident about this. Hopefully folks can take a look at > it. > > In general, patches earlier in this series should be "less > controversial" and hopefully can land even if people don't like > patches later in the series. ;-) > > Looking back, this is pretty much two series squashed that could be > treated indepdently. The first is a serial series and the second is a > kgdb series. > > For all serial patches I'd expect them to go through the tty tree once > they've been reviewed. > > If folks are OK w/ the 'smp' patch it probably should go in some core > kernel tree. The kgdb patch won't work without it, though, so to land > that we'd need coordination between the folks landing that and the > folks landing the 'smp' patch. I have got only 0/7 and 5/7, everything okay with your mail client and other tools? > > > Douglas Anderson (7): > 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 > smp: Don't yell about IRQs disabled in kgdb_roundup_cpus() > kgdb: Remove irq flags and local_irq_enable/disable from roundup > > arch/arc/kernel/kgdb.c | 4 +-- > arch/arm/kernel/kgdb.c | 4 +-- > arch/arm64/kernel/kgdb.c | 4 +-- > arch/hexagon/kernel/kgdb.c | 11 ++---- > arch/mips/kernel/kgdb.c | 4 +-- > arch/powerpc/kernel/kgdb.c | 2 +- > arch/sh/kernel/kgdb.c | 4 +-- > arch/sparc/kernel/smp_64.c | 2 +- > arch/x86/kernel/kgdb.c | 9 ++--- > 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/kgdb.h | 9 ++--- > include/linux/serial_core.h | 38 ++++++++++++++++++++- > kernel/debug/debug_core.c | 2 +- > kernel/smp.c | 4 ++- > 18 files changed, 80 insertions(+), 53 deletions(-) > > -- > 2.19.1.568.g152ad8e336-goog > -- With Best Regards, Andy Shevchenko