> On Sep 1, 2023, at 7:05 PM, Brook Milligan <br...@nmsu.edu> wrote: > >> On Sep 1, 2023, at 5:33 PM, Brett Lymn <bl...@internode.on.net> wrote: >> >> On Thu, Aug 31, 2023 at 09:02:53PM -0600, Brook Milligan wrote: >>> >>> However, a write fails and hangs the board hard: no keyboard response, no >>> response to pings. I have attached the test program below, and would >>> appreciate more eyes on it from (the many) people who obviously know serial >>> line programming better than I do. It gets as far as the write() call, but >>> no further. >>> >> >> This sounds like a driver bug. In no circumstances should a user land >> program be able to >> hang a machine. I would log a kernel PR with your sample code attached.
I’ll submit a PR; what category? This is likely a kernel bug (so kern?) but it
applies to the Beaglebone Black (so port-evbarm?). I’m thinking the former.
The bug is easy to replicate with just a native installation. I have attached
a file (kernel-hang.tgz) with the necessary bits.
- am335x-boneblack-comm_cape.dtb: a binary device tree file that can be loaded
when booting a Beaglebone Black. See below. This enables the uart4 as
intended for the Beaglebone comms cape, but the cape is not required.
- am335x-boneblack-comm_cape.dts: a device tree source file that enables uart4
as intended for the Beaglebone comms cape. It includes the
am335x-boneblack.dts file, which is the default for the Beaglebone Black. As a
result, the only differences are the few lines in this file.
- am335x-bone-common.dtsi.patch: a patch to replace /include/ with #include so
the C preprocessor is happy with all the files.
- am335x-boneblack-comm_cape.dts.pp: the result of running the C preprocessor
on am335x-boneblack-comm_cape.dts.
- Makefile: a makefile with two targets: patch and all used to make the other
files. The “patch” target applies the patch and the “all” target runs the C
preprocessor and dtc. Note that ${NETBSD_SRCDIR} should point to the root of
the NetBSD source.
Replicating the kernel hang:
- Add the binary device file am335x-boneblack-comm_cape.dtb to /boot/dtb/ on a
Beaglebone Black, so that it is available for the next boot.
- Boot into the U-Boot console, i.e., type space in the serial console
immediately when U-Boot begins the boot process.
- Enter the following commands into the U-Boot console; this will boot the
board with the new device tree:
setenv bootargs "root=ld0a”
fatload mmc 0:1 $kernel_addr_r netbsd-GENERIC.ub
fatload mmc 0:1 $fdt_addr_r dtb/am335x-boneblack-comm_cape.dtb
bootm $kernel_addr_r - $fdt_addr_r
- When the kernel boots into multiuser, run cu as
# cu -l /dev/tty01
This should report “Connected”. As soon as a character is typed into cu, the
kernel will hang.
I would greatly appreciate input on how to address this.
Thanks a lot.
Cheers,
Brook
kernel-hang.tgz
Description: Binary data
