Re: route cache DoS testing and softirqs

On Wed, Mar 31, 2004 at 11:31:09PM +0200, Andrea Arcangeli wrote:

On Thu, Apr 01, 2004 at 02:16:11AM +0530, Dipankar Sarma wrote:

quoted

I don't do any of this. I just have a separate quiescent state counter
for softirq RCU. It is incremented for regular quiescent points
like cswitch, userland, idle loop as well as at the completion
of each softirq handler. call_rcu_bh() uses its own queues.
Everything else works like call_rcu().

the point is that you want this counter to increase in every cpu quick,
that's why I was thinking at posting the tasklet, if the counter doesn't
increase from softirq, you fallback in the grace period length of the
non-bh rcu.

maybe the softirq load is so high in all cpus that just the additional
counter will fix it w/o having to post any additional tasklet (I very
much hope so but especially with irq binding I don't see it happening,
however with irq binding you may have a call_rcu_bh_cpuset).  You should
give it a try and see if it just works.

Ah, forcing CPUs for quiescent state is my last WMD if I have to use it ever :)

Thanks
Dipankar