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Re: IRQ interrupt at highest priority


>>>>> "Amlan" == Amlan Chakraborty <amlan.cha@wipro.com> writes:

Amlan> Thanx for the prompt response. I am extremely sorry for not
Amlan> being explicit. Specifically my queries are:

Amlan> 1) Will a lower priority interrupt under execution get
Amlan> pre-empted when a higher priority interrupt arrives?

Yes, if the HAL supports it and the appropriate option is
enabled. See CYGSEM_HAL_COMMON_INTERRUPTS_ALLOW_NESTING 

Amlan> 2) I found in file packages/kernel/.../src/common/clock.cxx ,
Amlan> the TIMER2 interrupt for the real-time clock ISR is created
Amlan> with priority 1 ( not the highest priority ). Hence when the
Amlan> real-time clock ISR is under execution will an interrupt of
Amlan> higher priority (say 0) pre-empt it?

Amlan> 3) Does ECOS internally use any other interrupt that is created
Amlan> with the highest priority (i.e. 0)?

eCos only uses the real-time clock. If it's created with priority 1,
it would be preempted by a level 0 interrupt, I guess.

Note however, that DSRs are not prioritized in the same manner (as far
as I remember). ISRs should all execute fairly fast, so being
interrupted by a ISR should not have much of an impact (unless it's
very frequent, obviously).

Jesper

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