[openib-general] [PATCH] mthca: eq doorbell coalescing + prevent even queque overrun

[Michael S. Tsirkin]

Quoting Or Gerlitz <ogerlitz at voltaire.com>:
> Subject: Re: [openib-general] [PATCH] mthca: eq doorbell coalescing + prevent even queque overrun
> 
> Michael S. Tsirkin wrote:
> >> Sorry, i dont follow. If you arm the CQ when there is one WC in it and 
> >> then start polling, and during your polling a "second" WC is generated 
> >> by the HCA, wouldn't an interrupt related to the 2nd completion be 
> >> generated - why the case you are mentioning is the arming window?
> 
> > I'm polling in the interrupt handler, so interrupts from the same IRQ are
> > disabled. No? What am I missing?
> 
> OK, i might be somehow newbee around this (working in hard irq context) 
> land. Does disabling the HCA IRQ means no interrupt would be generated 
> later when the handler is done? i was think it would be just deffered.

AFAIK, you get another interrupt only if hardware continues asserting
the interrupt.

> iSER hard irq CQ handler just does a context jump to soft irq handler 
> (tasklet) so the rule you mention does not apply to it.
> 

-- 
MST