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inetpeer: __rcu annotations
Adds __rcu annotations to inetpeer (struct inet_peer)->avl_left (struct inet_peer)->avl_right This is a tedious cleanup, but removes one smp_wmb() from link_to_pool() since we now use more self documenting rcu_assign_pointer(). Note the use of RCU_INIT_POINTER() instead of rcu_assign_pointer() in all cases we dont need a memory barrier. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
David S. Miller
parent
7a2b03c517
commit
b914c4ea92
@ -15,7 +15,7 @@
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struct inet_peer {
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/* group together avl_left,avl_right,v4daddr to speedup lookups */
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struct inet_peer *avl_left, *avl_right;
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struct inet_peer __rcu *avl_left, *avl_right;
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__be32 v4daddr; /* peer's address */
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__u32 avl_height;
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struct list_head unused;
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@ -72,18 +72,19 @@ static struct kmem_cache *peer_cachep __read_mostly;
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#define node_height(x) x->avl_height
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#define peer_avl_empty ((struct inet_peer *)&peer_fake_node)
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#define peer_avl_empty_rcu ((struct inet_peer __rcu __force *)&peer_fake_node)
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static const struct inet_peer peer_fake_node = {
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.avl_left = peer_avl_empty,
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.avl_right = peer_avl_empty,
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.avl_left = peer_avl_empty_rcu,
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.avl_right = peer_avl_empty_rcu,
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.avl_height = 0
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};
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static struct {
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struct inet_peer *root;
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struct inet_peer __rcu *root;
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spinlock_t lock;
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int total;
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} peers = {
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.root = peer_avl_empty,
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.root = peer_avl_empty_rcu,
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.lock = __SPIN_LOCK_UNLOCKED(peers.lock),
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.total = 0,
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};
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@ -156,11 +157,14 @@ static void unlink_from_unused(struct inet_peer *p)
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*/
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#define lookup(_daddr, _stack) \
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({ \
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struct inet_peer *u, **v; \
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struct inet_peer *u; \
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struct inet_peer __rcu **v; \
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\
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stackptr = _stack; \
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*stackptr++ = &peers.root; \
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for (u = peers.root; u != peer_avl_empty; ) { \
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for (u = rcu_dereference_protected(peers.root, \
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lockdep_is_held(&peers.lock)); \
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u != peer_avl_empty; ) { \
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if (_daddr == u->v4daddr) \
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break; \
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if ((__force __u32)_daddr < (__force __u32)u->v4daddr) \
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@ -168,7 +172,8 @@ static void unlink_from_unused(struct inet_peer *p)
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else \
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v = &u->avl_right; \
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*stackptr++ = v; \
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u = *v; \
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u = rcu_dereference_protected(*v, \
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lockdep_is_held(&peers.lock)); \
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} \
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u; \
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})
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@ -209,13 +214,17 @@ static struct inet_peer *lookup_rcu_bh(__be32 daddr)
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/* Called with local BH disabled and the pool lock held. */
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#define lookup_rightempty(start) \
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({ \
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struct inet_peer *u, **v; \
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struct inet_peer *u; \
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struct inet_peer __rcu **v; \
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*stackptr++ = &start->avl_left; \
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v = &start->avl_left; \
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for (u = *v; u->avl_right != peer_avl_empty; ) { \
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for (u = rcu_dereference_protected(*v, \
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lockdep_is_held(&peers.lock)); \
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u->avl_right != peer_avl_empty_rcu; ) { \
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v = &u->avl_right; \
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*stackptr++ = v; \
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u = *v; \
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u = rcu_dereference_protected(*v, \
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lockdep_is_held(&peers.lock)); \
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} \
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u; \
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})
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@ -224,74 +233,86 @@ static struct inet_peer *lookup_rcu_bh(__be32 daddr)
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* Variable names are the proof of operation correctness.
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* Look into mm/map_avl.c for more detail description of the ideas.
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*/
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static void peer_avl_rebalance(struct inet_peer **stack[],
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struct inet_peer ***stackend)
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static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
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struct inet_peer __rcu ***stackend)
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{
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struct inet_peer **nodep, *node, *l, *r;
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struct inet_peer __rcu **nodep;
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struct inet_peer *node, *l, *r;
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int lh, rh;
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while (stackend > stack) {
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nodep = *--stackend;
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node = *nodep;
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l = node->avl_left;
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r = node->avl_right;
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node = rcu_dereference_protected(*nodep,
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lockdep_is_held(&peers.lock));
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l = rcu_dereference_protected(node->avl_left,
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lockdep_is_held(&peers.lock));
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r = rcu_dereference_protected(node->avl_right,
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lockdep_is_held(&peers.lock));
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lh = node_height(l);
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rh = node_height(r);
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if (lh > rh + 1) { /* l: RH+2 */
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struct inet_peer *ll, *lr, *lrl, *lrr;
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int lrh;
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ll = l->avl_left;
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lr = l->avl_right;
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ll = rcu_dereference_protected(l->avl_left,
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lockdep_is_held(&peers.lock));
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lr = rcu_dereference_protected(l->avl_right,
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lockdep_is_held(&peers.lock));
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lrh = node_height(lr);
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if (lrh <= node_height(ll)) { /* ll: RH+1 */
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node->avl_left = lr; /* lr: RH or RH+1 */
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node->avl_right = r; /* r: RH */
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RCU_INIT_POINTER(node->avl_left, lr); /* lr: RH or RH+1 */
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RCU_INIT_POINTER(node->avl_right, r); /* r: RH */
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node->avl_height = lrh + 1; /* RH+1 or RH+2 */
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l->avl_left = ll; /* ll: RH+1 */
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l->avl_right = node; /* node: RH+1 or RH+2 */
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RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH+1 */
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RCU_INIT_POINTER(l->avl_right, node); /* node: RH+1 or RH+2 */
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l->avl_height = node->avl_height + 1;
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*nodep = l;
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RCU_INIT_POINTER(*nodep, l);
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} else { /* ll: RH, lr: RH+1 */
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lrl = lr->avl_left; /* lrl: RH or RH-1 */
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lrr = lr->avl_right; /* lrr: RH or RH-1 */
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node->avl_left = lrr; /* lrr: RH or RH-1 */
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node->avl_right = r; /* r: RH */
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lrl = rcu_dereference_protected(lr->avl_left,
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lockdep_is_held(&peers.lock)); /* lrl: RH or RH-1 */
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lrr = rcu_dereference_protected(lr->avl_right,
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lockdep_is_held(&peers.lock)); /* lrr: RH or RH-1 */
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RCU_INIT_POINTER(node->avl_left, lrr); /* lrr: RH or RH-1 */
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RCU_INIT_POINTER(node->avl_right, r); /* r: RH */
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node->avl_height = rh + 1; /* node: RH+1 */
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l->avl_left = ll; /* ll: RH */
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l->avl_right = lrl; /* lrl: RH or RH-1 */
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RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH */
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RCU_INIT_POINTER(l->avl_right, lrl); /* lrl: RH or RH-1 */
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l->avl_height = rh + 1; /* l: RH+1 */
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lr->avl_left = l; /* l: RH+1 */
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lr->avl_right = node; /* node: RH+1 */
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RCU_INIT_POINTER(lr->avl_left, l); /* l: RH+1 */
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RCU_INIT_POINTER(lr->avl_right, node); /* node: RH+1 */
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lr->avl_height = rh + 2;
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*nodep = lr;
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RCU_INIT_POINTER(*nodep, lr);
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}
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} else if (rh > lh + 1) { /* r: LH+2 */
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struct inet_peer *rr, *rl, *rlr, *rll;
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int rlh;
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rr = r->avl_right;
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rl = r->avl_left;
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rr = rcu_dereference_protected(r->avl_right,
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lockdep_is_held(&peers.lock));
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rl = rcu_dereference_protected(r->avl_left,
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lockdep_is_held(&peers.lock));
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rlh = node_height(rl);
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if (rlh <= node_height(rr)) { /* rr: LH+1 */
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node->avl_right = rl; /* rl: LH or LH+1 */
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node->avl_left = l; /* l: LH */
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RCU_INIT_POINTER(node->avl_right, rl); /* rl: LH or LH+1 */
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RCU_INIT_POINTER(node->avl_left, l); /* l: LH */
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node->avl_height = rlh + 1; /* LH+1 or LH+2 */
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r->avl_right = rr; /* rr: LH+1 */
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r->avl_left = node; /* node: LH+1 or LH+2 */
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RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH+1 */
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RCU_INIT_POINTER(r->avl_left, node); /* node: LH+1 or LH+2 */
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r->avl_height = node->avl_height + 1;
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*nodep = r;
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RCU_INIT_POINTER(*nodep, r);
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} else { /* rr: RH, rl: RH+1 */
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rlr = rl->avl_right; /* rlr: LH or LH-1 */
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rll = rl->avl_left; /* rll: LH or LH-1 */
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node->avl_right = rll; /* rll: LH or LH-1 */
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node->avl_left = l; /* l: LH */
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rlr = rcu_dereference_protected(rl->avl_right,
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lockdep_is_held(&peers.lock)); /* rlr: LH or LH-1 */
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rll = rcu_dereference_protected(rl->avl_left,
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lockdep_is_held(&peers.lock)); /* rll: LH or LH-1 */
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RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */
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RCU_INIT_POINTER(node->avl_left, l); /* l: LH */
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node->avl_height = lh + 1; /* node: LH+1 */
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r->avl_right = rr; /* rr: LH */
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r->avl_left = rlr; /* rlr: LH or LH-1 */
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RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH */
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RCU_INIT_POINTER(r->avl_left, rlr); /* rlr: LH or LH-1 */
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r->avl_height = lh + 1; /* r: LH+1 */
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rl->avl_right = r; /* r: LH+1 */
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rl->avl_left = node; /* node: LH+1 */
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RCU_INIT_POINTER(rl->avl_right, r); /* r: LH+1 */
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RCU_INIT_POINTER(rl->avl_left, node); /* node: LH+1 */
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rl->avl_height = lh + 2;
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*nodep = rl;
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RCU_INIT_POINTER(*nodep, rl);
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}
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} else {
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node->avl_height = (lh > rh ? lh : rh) + 1;
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@ -303,10 +324,10 @@ static void peer_avl_rebalance(struct inet_peer **stack[],
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#define link_to_pool(n) \
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do { \
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n->avl_height = 1; \
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n->avl_left = peer_avl_empty; \
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n->avl_right = peer_avl_empty; \
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smp_wmb(); /* lockless readers can catch us now */ \
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**--stackptr = n; \
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n->avl_left = peer_avl_empty_rcu; \
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n->avl_right = peer_avl_empty_rcu; \
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/* lockless readers can catch us now */ \
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rcu_assign_pointer(**--stackptr, n); \
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peer_avl_rebalance(stack, stackptr); \
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} while (0)
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@ -330,24 +351,25 @@ static void unlink_from_pool(struct inet_peer *p)
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* We use refcnt=-1 to alert lockless readers this entry is deleted.
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*/
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if (atomic_cmpxchg(&p->refcnt, 1, -1) == 1) {
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struct inet_peer **stack[PEER_MAXDEPTH];
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struct inet_peer ***stackptr, ***delp;
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struct inet_peer __rcu **stack[PEER_MAXDEPTH];
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struct inet_peer __rcu ***stackptr, ***delp;
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if (lookup(p->v4daddr, stack) != p)
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BUG();
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delp = stackptr - 1; /* *delp[0] == p */
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if (p->avl_left == peer_avl_empty) {
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if (p->avl_left == peer_avl_empty_rcu) {
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*delp[0] = p->avl_right;
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--stackptr;
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} else {
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/* look for a node to insert instead of p */
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struct inet_peer *t;
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t = lookup_rightempty(p);
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BUG_ON(*stackptr[-1] != t);
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BUG_ON(rcu_dereference_protected(*stackptr[-1],
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lockdep_is_held(&peers.lock)) != t);
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**--stackptr = t->avl_left;
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/* t is removed, t->v4daddr > x->v4daddr for any
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* x in p->avl_left subtree.
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* Put t in the old place of p. */
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*delp[0] = t;
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RCU_INIT_POINTER(*delp[0], t);
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t->avl_left = p->avl_left;
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t->avl_right = p->avl_right;
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t->avl_height = p->avl_height;
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@ -414,7 +436,7 @@ static int cleanup_once(unsigned long ttl)
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struct inet_peer *inet_getpeer(__be32 daddr, int create)
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{
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struct inet_peer *p;
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struct inet_peer **stack[PEER_MAXDEPTH], ***stackptr;
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struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
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/* Look up for the address quickly, lockless.
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* Because of a concurrent writer, we might not find an existing entry.
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