lkml.org 
[lkml]   [2008]   [Aug]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 2/2] smp_call_function: use rwlocks on queues rather than rcu
From
Date
On Mon, 2008-08-25 at 10:46 -0500, Christoph Lameter wrote:
> Peter Zijlstra wrote:
> >
> > If we combine these two cases, and flip the counter as soon as we've
> > enqueued one callback, unless we're already waiting for a grace period
> > to end - which gives us a longer window to collect callbacks.
> >
> > And then the rcu_read_unlock() can do:
> >
> > if (dec_and_zero(my_counter) && my_index == dying)
> > raise_softirq(RCU)
> >
> > to fire off the callback stuff.
> >
> > /me ponders - there must be something wrong with that...
> >
> > Aaah, yes, the dec_and_zero is non trivial due to the fact that its a
> > distributed counter. Bugger..
>
> Then lets make it per cpu. If we get the cpu ops in then dec_and_zero would be
> very cheap.

Hmm, perhaps that might work for classic RCU, as that disables
preemption and thus the counters should always be balanced.



\
 
 \ /
  Last update: 2008-08-25 17:55    [W:0.112 / U:5.316 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site