Thanks, will look into it in more detail. Perhaps figuring out how to do
oprofile without sleeping would be best.
On Thu, 2002-12-19 at 04:49, Vamsi Krishna S . wrote:
> Hi Stephen,
>
> On Wed, Dec 18, 2002 at 11:06:08PM +0000, Stephen Hemminger wrote:
> > The notifier interface was only partially locked. The
> > notifier_call_chain needs to be called in places where it is impossible
> > to safely without having deadlocks; for example, NMI watchdog timeout.
> >
> > This patch uses read-copy-update to manage the list. One extra bit of
> > safety is using a reference count on the notifier_blocks to allow for
> > cases like oprofile which need to sleep in a callback.
> >
> <snip>
> >
> > int notifier_call_chain(struct list_head *list, unsigned long val, void
> > *v)
> > {
> > - struct list_head *p;
> > + struct list_head *p, *nxtp;
> > int ret = NOTIFY_DONE;
> >
> > - list_for_each(p, list) {
> > + rcu_read_lock();
> > + list_for_each_safe_rcu(p, nxtp, list) {
> > struct notifier_block *nb =
> > list_entry(p, struct notifier_block, link);
> >
> > + atomic_inc(&nb->inuse);
> > ret = nb->notifier_call(nb,val,v);
> > + atomic_dec(&nb->inuse);
> > +
>
> There could be a small problem here. When rcu_read_lock() is called,
> it bumps the preempt_count, so when the called handler attempts
> to sleep, it will oops with "Bad: scheduling in atomic region".
-- Stephen Hemminger <shemminger@osdl.org> Open Source Devlopment Lab- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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