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In order to use kgdb you must activate it by passing configuration information to one of the kgdb I/O drivers. If you do not pass any configuration information kgdb will not do anything at all. Kgdb will only actively hook up to the kernel trap hooks if a kgdb I/O driver is loaded and configured. If you unconfigure a kgdb I/O driver, kgdb will unregister all the kernel hook points.
All drivers can be reconfigured at run time, if
CONFIG_SYSFS and CONFIG_MODULES
are enabled, by echo'ing a new config string to
/sys/module/<driver>/parameter/<option>.
The driver can be unconfigured by passing an empty string. You cannot
change the configuration while the debugger is attached. Make sure
to detach the debugger with the detach command
prior to trying unconfigure a kgdb I/O driver.
The Kernel command line option kgdbwait makes
kgdb wait for a debugger connection during booting of a kernel. You
can only use this option you compiled a kgdb I/O driver into the
kernel and you specified the I/O driver configuration as a kernel
command line option. The kgdbwait parameter should always follow the
configuration parameter for the kgdb I/O driver in the kernel
command line else the I/O driver will not be configured prior to
asking the kernel to use it to wait.
The kernel will stop and wait as early as the I/O driver and architecture will allow when you use this option. If you build the kgdb I/O driver as a kernel module kgdbwait will not do anything.