Re: [RFC&PATCH] Alternative RCU implementation

Jim Houston
2004-09-01T00:17:13Z

On Mon, 2004-08-30 at 13:38, Dipankar Sarma wrote:

> > I'm also trying to figure out if I need the call_rcu_bh() changes.
> > Since my patch will recognize a grace periods as soon as any
> > pending read-side critical sections complete, I suspect that I
> > don't need this change.
>
> Except that under a softirq flood, a reader in a different read-side
> critical section may get delayed a lot holding up RCU. Let me know
> if I am missing something here.

Hi Dipankar,

O.k. That makes sense. So the rcu_read_lock_bh(), rcu_read_unlock_bh()
and call_rcu_bh() would be the preferred interface. Are there cases
where they can't be used? How do you decide where to use the _bh
flavor?

I see that local_bh_enable() WARNS if interrupts are disabled. Is that
the issue? Are rcu_read_lock()/rcu_read_unlock() ever called from
code which disables interrupts?

Jim Houston - Concurrent Computer Corp.