RTEMS Porting Guide
The CPU_MODES_INTERRUPT_MASK macro defines the number of bits actually used in the interrupt field of the task mode. How those bits map to the CPU interrupt levels is defined by the routine _CPU_ISR_Set_level().
The following illustrates how the CPU_MODES_INTERRUPT_MASK is set on a CPU family like the Intel i386 where the CPU itself only recognizes two interrupt levels - enabled and disabled.
#define CPU_MODES_INTERRUPT_MASK 0x00000001
RTEMS Porting Guide
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