Re: [PATCH] qe_ic: Do a sync when masking interrupts.

Kumar Gala wrote:

On Oct 23, 2006, at 10:19 AM, Scott Wood wrote:

quoted

Possibly -- but the only problem on the rare occasions where the  timing
is not fortuitous is a spurious interrupt; the only reason the sync
needs to be there at all is to avoid the overhead of the extra  interrupt
(and to avoid user complaints that they're getting "BAD" interrupts).

Why wouldn't the read accomplish the same thing in a more robust way  
than the sync?

It would.  However, it also adds a small amount of overhead to every QE 
interrupt, and the only thing that that overhead buys is avoiding 
possible but empirically very rare spurious interrupts; it'd cost more 
than simply accepting that a spurious interrupt might happen once in a 
great while.

Without any type of sync, spurious interrupts happen fairly regularly 
(about 5-10% of legitimate interrupts), so adding the sync should be a 
net gain over doing nothing.

If the consensus is that a read should be done anyway, I can resumbit 
the patch that way; I just think it's overkill given that a 100% 
guarantee isn't required for correctness.

-Scott