tipc: let group member stay in JOINED mode if unable to reclaim (4ea5dab5) · Commits · 戴 / test

We handle a corner case in the function tipc_group_update_rcv_win(). During extreme pessure it might happen that a message receiver has all its active senders in RECLAIMING or REMITTED mode, meaning that there is nobody to reclaim advertisements from if an additional sender tries to go active. Currently we just set the new sender to ACTIVE anyway, hence at least theoretically opening up for a receiver queue overflow by exceeding the MAX_ACTIVE limit. The correct solution to this is to instead add the member to the pending queue, while letting the oldest member in that queue revert to JOINED state. In this commit we refactor the code for handling message arrival from a JOINED member, both to make it more comprehensible and to cover the case described above. Acked-by:

Ying Xue <ying.xue@windriver.com> Signed-off-by:

Jon Maloy <jon.maloy@ericsson.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/tipc/group.c

+22 −12

Original line number	Diff line number	Diff line
		@@ -569,24 +569,34 @@ void tipc_group_update_rcv_win(struct tipc_group *grp, int blks, u32 node,

		switch (m->state) {
		case MBR_JOINED:
		/* Reclaim advertised space from least active member */
		if (!list_empty(active) && active_cnt >= reclaim_limit) {
		/* First, decide if member can go active */
		if (active_cnt <= max_active) {
		m->state = MBR_ACTIVE;
		list_add_tail(&m->list, active);
		grp->active_cnt++;
		tipc_group_proto_xmit(grp, m, GRP_ADV_MSG, xmitq);
		} else {
		m->state = MBR_PENDING;
		list_add_tail(&m->list, &grp->pending);
		}

		if (active_cnt < reclaim_limit)
		break;

		/* Reclaim from oldest active member, if possible */
		if (!list_empty(active)) {
		rm = list_first_entry(active, struct tipc_member, list);
		rm->state = MBR_RECLAIMING;
		list_del_init(&rm->list);
		tipc_group_proto_xmit(grp, rm, GRP_RECLAIM_MSG, xmitq);
		}
		/* If max active, become pending and wait for reclaimed space */
		if (active_cnt >= max_active) {
		m->state = MBR_PENDING;
		list_add_tail(&m->list, &grp->pending);
		break;
		}
		/* Otherwise become active */
		m->state = MBR_ACTIVE;
		list_add_tail(&m->list, &grp->active);
		grp->active_cnt++;
		/* Fall through */
		/* Nobody to reclaim from; - revert oldest pending to JOINED */
		pm = list_first_entry(&grp->pending, struct tipc_member, list);
		list_del_init(&pm->list);
		pm->state = MBR_JOINED;
		tipc_group_proto_xmit(grp, pm, GRP_ADV_MSG, xmitq);
		break;
		case MBR_ACTIVE:
		if (!list_is_last(&m->list, &grp->active))
		list_move_tail(&m->list, &grp->active);

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