13.2 Sysinit Operation

Sysinit relies on the ability of the linker to take static data declared at multiple locations throughout a program's source and group it together as a single contiguous chunk of data. This linker technique is called a ``linker set''. Sysinit uses two linker sets to maintain two data sets containing each consumer's call order, function, and a pointer to the data to pass to that function.

Sysinit uses two priorities when ordering the functions for execution. The first priority is a subsystem ID giving an overall order Sysinit's dispatch of functions. Current predeclared ID's are in <sys/kernel.h> in the enum list sysinit_sub_id. The second priority used is an element order within the subsystem. Current predeclared subsystem element orders are in <sys/kernel.h> in the enum list sysinit_elem_order.

There are currently two uses for Sysinit. Function dispatch at system startup and kernel module loads, and function dispatch at system shutdown and kernel module unload.