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| author | Dmitry Safonov <dima@arista.com> | 2020-03-02 17:51:35 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-03-07 09:52:02 +0100 |
| commit | 68af43173d3fcece70bef49cb992c64c4c68ff23 (patch) | |
| tree | afb70c4f7e9f9502e4afcbc896f43155ebc7571c /lib/Kconfig.debug | |
| parent | eaee41727e6d8a7d2b94421c25e82b00cb2fded5 (diff) | |
| download | lwn-68af43173d3fcece70bef49cb992c64c4c68ff23.tar.gz lwn-68af43173d3fcece70bef49cb992c64c4c68ff23.zip | |
serial/sysrq: Add MAGIC_SYSRQ_SERIAL_SEQUENCE
Many embedded boards have a disconnected TTL level serial which can
generate some garbage that can lead to spurious false sysrq detects.
Currently, sysrq can be either completely disabled for serial console
or always disabled (with CONFIG_MAGIC_SYSRQ_SERIAL), since
commit 732dbf3a6104 ("serial: do not accept sysrq characters via serial port")
At Arista, we have such boards that can generate BREAK and random
garbage. While disabling sysrq for serial console would solve
the problem with spurious false sysrq triggers, it's also desirable
to have a way to enable sysrq back.
As a measure of balance between on and off options, add
MAGIC_SYSRQ_SERIAL_SEQUENCE which is a string sequence that can enable
sysrq if it follows BREAK on a serial line. The longer the string - the
less likely it may be in the garbage.
Having the way to enable sysrq was beneficial to debug lockups with
a manual investigation in field and on the other side preventing false
sysrq detections.
Based-on-patch-by: Vasiliy Khoruzhick <vasilykh@arista.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200302175135.269397-3-dima@arista.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib/Kconfig.debug')
| -rw-r--r-- | lib/Kconfig.debug | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 69def4a9df00..38a8f3c99579 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -431,6 +431,14 @@ config MAGIC_SYSRQ_SERIAL This option allows you to decide whether you want to enable the magic SysRq key. +config MAGIC_SYSRQ_SERIAL_SEQUENCE + string "Char sequence that enables magic SysRq over serial" + depends on MAGIC_SYSRQ_SERIAL + default "" + help + Specifies a sequence of characters that can follow BREAK to enable + SysRq on a serial console. + config DEBUG_FS bool "Debug Filesystem" help |