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

Lee Revell rlrevell at joe-job.com
Sun Nov 27 16:58:12 EST 2005

On Sun, 2005-11-27 at 13:12 -0800, Mark Knecht wrote:
> Sorry, but while this is correct at the software level it is,
> unfortunately, completely incorrect at the hardware level. While I am
> not a programmer and do not know myself how to do it, if I write (as
> an example only) an ISR that simply turns off interrupts and goes into
> a loop, then since interrupts are off no other interrupt will get
> through and since the ISR is in a loop it will never return. The
> machine is locked and you're hung.
> While I do not suggest that this example is anything other than
> pathological, it demonstrates the problem. 

It does not demonstrate a real world problem.  If this were to happen it
would be a grave kernel bug.

In the Linux kernel only drivers that register their ISR with
SA_INTERRUPT block out ALL other interrupts until they complete.
Currently the ALSA drivers and system timer do this as the handling of
those interrupts has RT constraints, and the handlers execute quickly


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