RTEMS 4.6.99.3 On-Line Library

Task Context Management Task Context

RTEMS Porting Guide

6.3: Task Context

Task Context Management Basic Context Data Structure

Task Context Management Initializing a Context

Task Context Management Performing a Context Switch

Task Context Management Restoring a Context

Task Context Management Restarting the Currently Executing Task

Associated with each task is a context that distinguishes it from other tasks in the system and logically gives it its own scratch pad area for computations. In addition, when an interrupt occurs some processor context information must be saved and restored. This is managed in RTEMS as three items:

Basic task level context (e.g. the Context_Control structure)
Floating point task context (e.g. Context_Control_fp structure)
Interrupt level context (e.g. the Context_Control_interrupt structure)

The integer and floating point context structures and the routines that manipulate them are discussed in detail in this section, while the interrupt level context structure is discussed in the XXX.

Additionally, if the GNU debugger gdb is to be made aware of RTEMS tasks for this CPU, then care should be used in designing the context area.

typedef struct {
    unsigned32 special_interrupt_register;
} CPU_Interrupt_frame;

RTEMS Porting Guide