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Commit eb929a91 authored by Jon Maloy's avatar Jon Maloy Committed by David S. Miller
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tipc: improve poll() for group member socket 



The current criteria for returning POLLOUT from a group member socket is
too simplistic. It basically returns POLLOUT as soon as the group has
external destinations, something obviously leading to a lot of spinning
during destination congestion situations. At the same time, the internal
congestion handling is unnecessarily complex.

We now change this as follows.

- We introduce an 'open' flag in  struct tipc_group. This flag is used
  only to help poll() get the setting of POLLOUT right, and *not* for
  congeston handling as such. This means that a user can choose to
  ignore an  EAGAIN for a destination and go on sending messages to
  other destinations in the group if he wants to.

- The flag is set to false every time we return EAGAIN on a send call.

- The flag is set to true every time any member, i.e., not necessarily
  the member that caused EAGAIN, is removed from the small_win list.

- We remove the group member 'usr_pending' flag. The size of the send
  window and presence in the 'small_win' list is sufficient criteria
  for recognizing congestion.

This solution seems to be a reasonable compromise between 'anycast',
which is normally not waiting for POLLOUT for a specific destination,
and the other three send modes, which are.

Acked-by: default avatarYing Xue <ying.xue@windriver.com>
Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 232d07b7

net/tipc/group.c

+36 −28
Original line number Diff line number Diff line
@@ -74,7 +74,6 @@ struct tipc_member { 
	u16 bc_rcv_nxt;

	u16 bc_syncpt;

	u16 bc_acked;

	bool usr_pending;

};



struct tipc_group {
@@ -96,11 +95,27 @@ struct tipc_group { 
	u16 bc_ackers;

	bool loopback;

	bool events;

	bool open;

};



static void tipc_group_proto_xmit(struct tipc_group *grp, struct tipc_member *m,

				  int mtyp, struct sk_buff_head *xmitq);



bool tipc_group_is_open(struct tipc_group *grp)

{

	return grp->open;

}



static void tipc_group_open(struct tipc_member *m, bool *wakeup)

{

	*wakeup = false;

	if (list_empty(&m->small_win))

		return;

	list_del_init(&m->small_win);

	m->group->open = true;

	*wakeup = true;

}



static void tipc_group_decr_active(struct tipc_group *grp,

				   struct tipc_member *m)

{
@@ -406,20 +421,20 @@ bool tipc_group_cong(struct tipc_group *grp, u32 dnode, u32 dport, 
	int adv, state;



	m = tipc_group_find_dest(grp, dnode, dport);

	*mbr = m;

	if (!m)

	if (!tipc_group_is_receiver(m)) {

		*mbr = NULL;

		return false;

	if (m->usr_pending)

		return true;

	}

	*mbr = m;



	if (m->window >= len)

		return false;

	m->usr_pending = true;



	grp->open = false;



	/* If not fully advertised, do it now to prevent mutual blocking */

	adv = m->advertised;

	state = m->state;

	if (state < MBR_JOINED)

		return true;

	if (state == MBR_JOINED && adv == ADV_IDLE)

		return true;

	if (state == MBR_ACTIVE && adv == ADV_ACTIVE)
@@ -437,9 +452,10 @@ bool tipc_group_bc_cong(struct tipc_group *grp, int len) 
	struct tipc_member *m = NULL;



	/* If prev bcast was replicast, reject until all receivers have acked */

	if (grp->bc_ackers)

	if (grp->bc_ackers) {

		grp->open = false;

		return true;



	}

	if (list_empty(&grp->small_win))

		return false;
@@ -754,9 +770,7 @@ void tipc_group_proto_rcv(struct tipc_group *grp, bool *usr_wakeup, 


		/* Member can be taken into service */

		m->state = MBR_JOINED;

		*usr_wakeup = true;

		m->usr_pending = false;

		list_del_init(&m->small_win);

		tipc_group_open(m, usr_wakeup);

		tipc_group_update_member(m, 0);

		tipc_group_proto_xmit(grp, m, GRP_ADV_MSG, xmitq);

		tipc_group_create_event(grp, m, TIPC_PUBLISHED,
@@ -767,8 +781,7 @@ void tipc_group_proto_rcv(struct tipc_group *grp, bool *usr_wakeup, 
			return;

		m->bc_syncpt = msg_grp_bc_syncpt(hdr);

		list_del_init(&m->list);

		list_del_init(&m->small_win);

		*usr_wakeup = true;

		tipc_group_open(m, usr_wakeup);

		tipc_group_decr_active(grp, m);

		m->state = MBR_LEAVING;

		tipc_group_create_event(grp, m, TIPC_WITHDRAWN,
@@ -778,26 +791,25 @@ void tipc_group_proto_rcv(struct tipc_group *grp, bool *usr_wakeup, 
		if (!m)

			return;

		m->window += msg_adv_win(hdr);

		*usr_wakeup = m->usr_pending;

		m->usr_pending = false;

		list_del_init(&m->small_win);

		tipc_group_open(m, usr_wakeup);

		return;

	case GRP_ACK_MSG:

		if (!m)

			return;

		m->bc_acked = msg_grp_bc_acked(hdr);

		if (--grp->bc_ackers)

			break;

			return;

		list_del_init(&m->small_win);

		m->group->open = true;

		*usr_wakeup = true;

		m->usr_pending = false;

		tipc_group_update_member(m, 0);

		return;

	case GRP_RECLAIM_MSG:

		if (!m)

			return;

		*usr_wakeup = m->usr_pending;

		m->usr_pending = false;

		tipc_group_proto_xmit(grp, m, GRP_REMIT_MSG, xmitq);

		m->window = ADV_IDLE;

		tipc_group_open(m, usr_wakeup);

		return;

	case GRP_REMIT_MSG:

		if (!m || m->state != MBR_RECLAIMING)
@@ -883,9 +895,7 @@ void tipc_group_member_evt(struct tipc_group *grp, 
		/* Member can be taken into service */

		m->instance = instance;

		m->state = MBR_JOINED;

		*usr_wakeup = true;

		m->usr_pending = false;

		list_del_init(&m->small_win);

		tipc_group_open(m, usr_wakeup);

		tipc_group_update_member(m, 0);

		tipc_group_proto_xmit(grp, m, GRP_JOIN_MSG, xmitq);

		tipc_group_create_event(grp, m, TIPC_PUBLISHED,
@@ -895,12 +905,10 @@ void tipc_group_member_evt(struct tipc_group *grp, 
		if (!m)

			break;



		*usr_wakeup = true;

		m->usr_pending = false;

		tipc_group_decr_active(grp, m);

		m->state = MBR_LEAVING;

		list_del_init(&m->list);

		list_del_init(&m->small_win);

		tipc_group_open(m, usr_wakeup);



		/* Only send event if no LEAVE message can be expected */

		if (!tipc_node_is_up(net, node))

net/tipc/group.h

+1 −1
Original line number Diff line number Diff line
@@ -67,9 +67,9 @@ void tipc_group_update_bc_members(struct tipc_group *grp, int len, bool ack); 
bool tipc_group_cong(struct tipc_group *grp, u32 dnode, u32 dport,

		     int len, struct tipc_member **m);

bool tipc_group_bc_cong(struct tipc_group *grp, int len);

bool tipc_group_is_open(struct tipc_group *grp);

void tipc_group_update_rcv_win(struct tipc_group *grp, int blks, u32 node,

			       u32 port, struct sk_buff_head *xmitq);

u16 tipc_group_bc_snd_nxt(struct tipc_group *grp);

void tipc_group_update_member(struct tipc_member *m, int len);

int tipc_group_size(struct tipc_group *grp);

#endif

net/tipc/socket.c

+4 −4
Original line number Diff line number Diff line
@@ -715,7 +715,7 @@ static unsigned int tipc_poll(struct file *file, struct socket *sock, 
{

	struct sock *sk = sock->sk;

	struct tipc_sock *tsk = tipc_sk(sk);

	struct tipc_group *grp = tsk->group;

	struct tipc_group *grp;

	u32 revents = 0;



	sock_poll_wait(file, sk_sleep(sk), wait);
@@ -736,8 +736,8 @@ static unsigned int tipc_poll(struct file *file, struct socket *sock, 
			revents |= POLLIN | POLLRDNORM;

		break;

	case TIPC_OPEN:

		if (!grp || tipc_group_size(grp))

			if (!tsk->cong_link_cnt)

		grp = tsk->group;

		if ((!grp || tipc_group_is_open(grp)) && !tsk->cong_link_cnt)

			revents |= POLLOUT;

		if (!tipc_sk_type_connectionless(sk))

			break;