[linux-audio-user] IRQ conflicts, acpi, and linux audio

Lee Revell rlrevell at joe-job.com
Sun Nov 27 16:59:43 EST 2005

On Sun, 2005-11-27 at 16:51 -0500, Paul Davis wrote:
> On Sun, 2005-11-27 at 15:07 -0500, Lee Revell wrote:
> > Wrong.  PIC or APIC, interrupts do not delay other interrupts in this
> > way.  If a disk interrupt happens on IRQ14 then a soundcard interrupt on
> > IRQ5 fires immediately after then the disk interrupt handler will be
> > interrupted by the sound card interrupt handler.  That's why they are
> > called interrupts!  This is why I keep trying to explain that there is
> > no "priority" relationship between interrupts.
> wrong, at least on PIC based systems. the PIC doesn't allow the IRQ line
> to the CPU to be raised by a lower priority line until the CPU has acked
> the higher priority IRQ. if the CPU never resets the relevant bit on the
> PIC, you can completely wedge the system. all linux kernels clear this
> bit long before the interrupt handler for the device is ever invoked, so
> you can be forgiven for thinking it works the way you've described :)

Ah, OK.  I should have prefaced my statement with "from the Linux
kernel's perspective".

Anyway my point (that the OP is not going to improve his PD performance
by twiddling with the interrupt controller) remains valid.


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