Disabling interrupts and masking interrupts

[Kevin Wilson]

Hi,
Are you sure about that Edge-triggered interrupts are gone and that
most hardware doesn't use edge triggers  ?
For example, on my x86_64, I get 9 edge interrupts:
  0:        127          0   IO-APIC-edge      timer
  1:          3          0   IO-APIC-edge      i8042
  4:          1          1   IO-APIC-edge
  8:          0          1   IO-APIC-edge      rtc0
 12:          1          3   IO-APIC-edge      i8042
 14:          0          0   IO-APIC-edge      ata_piix
 15:          0          0   IO-APIC-edge      ata_piix
 43:      30897          7   PCI-MSI-edge      em1
 44:        306        308   PCI-MSI-edge      snd_hda_intel

Also I remember I saw in a book about Kernel that edge interrupts are
more common than level interrupts.
rgs
Kevin

On Thu, Mar 7, 2013 at 6:53 PM,  <Valdis.Kletnieks at vt.edu> wrote:
> On Thu, 07 Mar 2013 17:17:19 +0200, Kevin Wilson said:
>
>> Does this mean that once you are disabling
>> interrupts, these interrupts are lost ?  even later, when we will
>> enable interrupts, the interrupts from the past that should have been
>> created (but interrupts were disabled at that time interval) are in
>> fact lost?
>
> Level-triggered interruots will go off once interrupts are re-enabled,
> assuming that the device has kept the level set and not given up and timed
> out.
>
> Edge-trittered interrupts are gone.  That's part of why most hardware
> doesn't use edge triggers - it's just too hard to guarantee proper device
> driver operation.
>
> Also, in common usage, "disabled interrupts" means that you're not listening
> to *any* interrupts, while "masked" means "we're not listening to *this*
> interrupt source, even if we *are* accepting interrupts from other sources".
>
> The difference is that sometimes the CPU is doing stuff that it would be
> potentially screwed if *any* interrupt happened, so we disable them.  Other
> times we're busy inside a device driver, and we're in a critical section
> for that device - but it's safe for other devices to interrupt.  So to improve
> latency we mask off just the one interrupt not all of them.