Re: [RFC PATCH net-next v3 9/9] net/smc: Add interface implementation of loopback device

[Wen Gu]

On 2023/2/22 22:09, Hillf Danton wrote:

> On Thu, 16 Feb 2023 00:18:25 +0800 Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
> > @@ -124,12 +126,76 @@ static int smc_lo_unregister_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb)
> >   	write_unlock(&ldev->dmb_ht_lock);
> >   
> >   	clear_bit(dmb_node->sba_idx, ldev->sba_idx_mask);
> > +
> > +	/* wait for dmb refcnt to be 0 */
> > +	if (!refcount_dec_and_test(&dmb_node->refcnt))
> > +		wait_event(ldev->dmbs_release, !refcount_read(&dmb_node->refcnt));
>
> Wait for zero refcnt with dmb node deleted from hash table.
>
> >   	kfree(dmb_node->cpu_addr);
> >   	kfree(dmb_node);
> >   
> > +	if (atomic_dec_and_test(&ldev->dmb_cnt))
> > +		wake_up(&ldev->ldev_release);
> > +	return 0;
> > +}
>
> [...]
>
> > +static int smc_lo_detach_dmb(struct smcd_dev *smcd, u64 token)
> > +{
> > +	struct smc_lo_dmb_node *dmb_node = NULL, *tmp_node;
> > +	struct smc_lo_dev *ldev = smcd->priv;
> > +
> > +	/* find dmb_node according to dmb->dmb_tok */
> > +	read_lock(&ldev->dmb_ht_lock);
> > +	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, token) {
> > +		if (tmp_node->token == token) {
> > +			dmb_node = tmp_node;
> > +			break;
> > +		}
> > +	}
> > +	if (!dmb_node) {
> > +		read_unlock(&ldev->dmb_ht_lock);
> > +		return -EINVAL;
> > +	}
> > +	read_unlock(&ldev->dmb_ht_lock);
> > +
> > +	if (refcount_dec_and_test(&dmb_node->refcnt))
> > +		wake_up_all(&ldev->dmbs_release);
> >   	return 0;
> >   }
>
> Given no wakeup without finding dmb node in hash table, the chance for
> missing wakeup is not zero.

Good catch! Will fix it.

Thanks,
Wen Gu