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cpu-supplement: Update interrupt stack paragraph

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Close #3459.
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Sebastian Huber 2018-07-18 08:14:09 +02:00
parent 4c2ca04c47
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cpu-supplement/port.rst
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@ -222,9 +222,9 @@ switches to this dedicated stack. On architectures without hardware support
for a dedicated interrupt stack which is separate from those of the tasks, for a dedicated interrupt stack which is separate from those of the tasks,
RTEMS will support switching to a dedicated stack for interrupt processing. RTEMS will support switching to a dedicated stack for interrupt processing.
Without a dedicated interrupt stack, every task in the system MUST have enough Without a dedicated interrupt stack, every task in the system must have enough
stack space to accommodate the worst case stack usage of that particular task stack space to accommodate the worst case stack usage of that particular task
and the interrupt service routines COMBINED. By supporting a dedicated and the interrupt service routines combined. By supporting a dedicated
interrupt stack, RTEMS significantly lowers the stack requirements for each interrupt stack, RTEMS significantly lowers the stack requirements for each
task. task.
@ -232,16 +232,20 @@ A nested interrupt is processed similarly with the exception that since the CPU
is already executing on the interrupt stack, there is no need to switch to the is already executing on the interrupt stack, there is no need to switch to the
interrupt stack. interrupt stack.
In some configurations, RTEMS allocates the interrupt stack from the Workspace The interrupt stacks (one for each configured processor) are statically
Area. The amount of memory allocated for the interrupt stack is user allocated by the application configuration via ``<rtems/confdefs.h>`` in the
configured and based upon the ``confdefs.h`` parameter special section ``.rtemsstack``. This enables an optimal placement of the
interrupt stacks by the Board Support Package (BSP), e.g. a fast on-chip
memory. The amount of memory allocated for each interrupt stack is user
configured and based upon the ``<rtems/confdefs.h>`` parameter
``CONFIGURE_INTERRUPT_STACK_SIZE``. This parameter is described in detail in ``CONFIGURE_INTERRUPT_STACK_SIZE``. This parameter is described in detail in
the Configuring a System chapter of the User's Guide. On configurations in the Configuring a System chapter of the User's Guide. Since interrupts are
which RTEMS allocates the interrupt stack, during the initialization process, disabled during the sequential system initialization and the
RTEMS will also install its interrupt stack. In other configurations, the ``_Thread_Start_multitasking()`` function does not return to the caller each
interrupt stack is allocated and installed by the Board Support Package (BSP). interrupt stack may be used for the initialization stack on the corresponding
processor.
In each of the architecture specific chapters, this section discesses the In each of the architecture specific chapters, this section discusses the
interrupt response and control mechanisms of the architecture as they pertain interrupt response and control mechanisms of the architecture as they pertain
to RTEMS. to RTEMS.