Re: [PATCH] Fixes for RCU handling of task_struct

["Paul E. McKenney" <paulmck@us.ibm.com>]

On Mon, Nov 07, 2005 at 12:12:25PM +1100, Nick Piggin wrote:
> Andrew Morton wrote:
> 
> >>+static inline int get_task_struct_rcu(struct task_struct *t)
> >>+{
> >>+	int oldusage;
> >>+
> >>+	do {
> >>+		oldusage = atomic_read(&t->usage);
> >>+		if (oldusage == 0) {
> >>+			return 0;
> >>+		}
> >>+	} while (cmpxchg(&t->usage.counter,
> >>+		 oldusage, oldusage + 1) != oldusage);
> >>+	return 1;
> >>+}
> >
> >
> >arm (at least) does not implement cmpxchg.
> >
> 
> Yes, and using atomic_t.counter in generic code is ugly, albeit
> compatible with all current implementations.
> 
> >I think Nick is working on patches which implement cmpxchg on all
> >architectures?
> 
> Yes, it is basically ready to go.

Would it simplify the rcuref.h code?  Or lib/dec_and_lock.c?

						Thanx, Paul