lkml.org 
[lkml]   [2010]   [Dec]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 2/4] genirq: Inform handler about line sharing state
Am 16.12.2010 14:13, Thomas Gleixner wrote:
> On Mon, 13 Dec 2010, Jan Kiszka wrote:
>> + if (old_action && (old_action->flags & IRQF_ADAPTIVE) &&
>> + !(desc->irq_data.drv_status & IRQS_SHARED)) {
>> + /*
>> + * Signal the old handler that is has to switch to shareable
>> + * handling mode. Disable the line to avoid any conflict with
>> + * a real IRQ.
>> + */
>> + disable_irq(irq);
>
> This is weird, really. I thought you wanted to avoid waiting for the
> threaded handler to finish if it's on the fly. So this should be
> disable_irq_nosync() or did you change your mind ?

No, I did not. I wanted to avoid that we set MAKE_SHAREABLE while there
might be another IRQ in flight. The handler that is called due to a real
IRQ might misinterpret MAKE_SHAREABLE as "there is no real event" and
perform the wrong steps (at least the current implementation for KVM would).

However, I will rebase my patch over your series now and try to re-think
this. The question is what could go wrong if we do not guarantee that
MAKE_SHAREABLE and ordinary IRQ will always be distinguishable. If there
is really nothing, specifically for the KVM scenario, we could even drop
the disable/enable_irq. That would be also be nicer when thinking about
potential delays of the already registered handler during this
transitional phase.

Jan

[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2010-12-16 21:29    [W:0.261 / U:0.352 seconds]
©2003-2014 Jasper Spaans. Advertise on this site