On 11/28/06, David Miller <[EMAIL PROTECTED]> wrote:
From: "Eric Lemoine" <[EMAIL PROTECTED]>
Date: Tue, 14 Nov 2006 22:54:40 +0100
> On 11/14/06, David Miller <[EMAIL PROTECTED]> wrote:
> > From: "Eric Lemoine" <[EMAIL PROTECTED]>
> > Date: Tue, 14 Nov 2006 08:28:42 +0100
> >
> > > because it makes it explicit that only bits 0 through 6 are taken into
> > > account when writing the IACK register.
> >
> > The phrase "bits 0 through 6" doesn't make any sense when bit 3 DOES
> > NOT EXIST in the hardware, it's reserved, it's not there, so including
> > it only confuses people and obfuscates the code.
> >
> > Please use the explicit bit mask composed of existing macros, which
> > not only makes sure that the mask has meaning, but it also makes sure
> > that reserved and non-existing bits are never referenced.
>
> Patch attached.
>
> Remember, the GEM_INTERRUPT_LOCKLESS isn't there to stay. It's
> currently there because I'm not sure the lockless implementation of
> gem_interrupt() will work with poll_net_controller.
>
> Thanks,
>
> Signed-off-by: Eric Lemoine <[EMAIL PROTECTED]>
This looks mostly fine.
I was thinking about the lockless stuff, and I wonder if there
is a clever way you can get it back down to one PIO on the
GREG_STAT register.
I think you'd need to have the ->poll() clear gp->status, then
do a smp_wb(), right before it re-enables interrupts.
Then in the interrupt handler, you need to find a way to safely
OR-in any unset bits in gp->status in a race-free manner.
I don't understand why we'd need all this.
I think the following code for gem_interrupt should do the trick:
static irqreturn_t gem_interrupt(int irq, void *dev_id)
{
struct net_device *dev = dev_id;
struct gem *gp = dev->priv;
unsigned int handled = 1;
if (!gp->running)
goto out;
if (netif_rx_schedule_prep(dev)) {
u32 gem_status = gem_read_status(gp);
gem_disable_ints();
if (unlikely(!gem_status))
handled = 0;
if (gem_irq_sync(gp)) {
netif_poll_enable(dev);
goto out;
}
gp->status = gem_status;
__netif_rx_schedule(dev);
}
out:
return IRQ_RETVAL(handled);
}
The important thing is: we __netif_rx_schedule even if gem_status is 0
(shared irq case) because we don't want to miss events should the
following scenario occur:
CPU0 CPU1
gem interrupt
prepare rx schedule
gem_interrupt
rx is
already scheduled
shared irq -> (we can miss NIC events
if we don't __netif_rx_schedule before
returning)
Thanks,
--
Eric
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