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Abort some questions of arm interrupt

josh zhao
Note: This was originally posted on 20th June 2008 at http://forums.arm.com

I try to understand arm interrupt,there are some questions I don't know,
  1.   Why the nested interrupt has to switch out of irq mode to svc mode?  I think  it only pushes the r14_irq into the irq stack.
   2.    The basic difference between a reentrant interrupt handler and a nested interrupt han-dler is that the interrupts are reenabled early on in the reentrant interrupt handler, which can reduce interrupt latency.
    I can't understand that ?

   thanks!
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  • 0 Arm Employee Badge
    Note: This was originally posted on 26th June 2008 at http://forums.arm.com

    Hi sim,
        For Interrupt nesting, I don't think interrupt A and interrupt B's handlers can be "active" at the same time. interrupt B must wait for returning by interrupt A if no interrupt occurs.


    Sorry, I used "active" to mean that an execution context for the two handlers existed concurrently, not that both handlers were actually being simultaneously worked upon; the typical case would be for the highest-prioirty handler to be run to completion before the lower priority one continues, though I could envisage other (more complicated) scenarios.

    hth
    s.
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  • 0 Arm Employee Badge
    Note: This was originally posted on 26th June 2008 at http://forums.arm.com

    Hi sim,
        For Interrupt nesting, I don't think interrupt A and interrupt B's handlers can be "active" at the same time. interrupt B must wait for returning by interrupt A if no interrupt occurs.


    Sorry, I used "active" to mean that an execution context for the two handlers existed concurrently, not that both handlers were actually being simultaneously worked upon; the typical case would be for the highest-prioirty handler to be run to completion before the lower priority one continues, though I could envisage other (more complicated) scenarios.

    hth
    s.
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