On Fri, Mar 18, 2005 at 05:17:29AM -0800, Bill Huey wrote:
> On Fri, Mar 18, 2005 at 04:56:41AM -0800, Bill Huey wrote:
> > On Thu, Mar 17, 2005 at 04:20:26PM -0800, Paul E. McKenney wrote:
> > > 5. Scalability -and- Realtime Response.
> > ...
> >
> > > void
> > > rcu_read_lock(void)
> > > {
> > > preempt_disable();
> > > if (current->rcu_read_lock_nesting++ == 0) {
> > > current->rcu_read_lock_ptr =
> > > &__get_cpu_var(rcu_data).lock;
> > > read_lock(current->rcu_read_lock_ptr);
> > > }
> > > preempt_enable();
> > > }
> >
> > Ok, here's a rather unsure question...
> >
> > Uh, is that a sleep violation if that is exclusively held since it
> > can block within an atomic critical section (deadlock) ?
>
> I'd like to note another problem. Mingo's current implementation of rt_mutex
> (super mutex for all blocking synchronization) is still missing reader counts
> and something like that would have to be implemented if you want to do
> priority
> inheritance over blocks.
>
> This is going to throw a wrench into your implementation if you assume that.
If we need to do priority inheritance across the memory allocator, so
that high-priority tasks blocked waiting for memory pass their priority
on to RCU readers, agreed. But I don't see any sign that real-time
preempt does this.
In absence of this, as Ingo noted, the fact that readers don't block
each other should make things be safe. I think...
Thanx, Paul
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