Re: [PATCH] Fixes for RCU handling of task_struct

[Nick Piggin]

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.

--
SUSE Labs, Novell Inc.

Send instant messages to your online friends http://au.messenger.yahoo.com 
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/