From: Mathieu Desnoyers Date: Mon, 27 May 2013 17:12:44 +0000 (-0400) Subject: Fix rcuja: concurrency checks X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=b62a8d0cdd624633182311ceabb532cd42088813;p=userspace-rcu.git Fix rcuja: concurrency checks add/delete need to re-check that RCU lookups are still valid after taking node locks. Signed-off-by: Mathieu Desnoyers --- diff --git a/rcuja/rcuja.c b/rcuja/rcuja.c index a5904ac..d24aaad 100644 --- a/rcuja/rcuja.c +++ b/rcuja/rcuja.c @@ -277,6 +277,7 @@ static struct cds_ja_inode_flag *ja_linear_node_get_nth(const struct cds_ja_type *type, struct cds_ja_inode *node, struct cds_ja_inode_flag ***child_node_flag_ptr, + struct cds_ja_inode_flag **child_node_flag_v, struct cds_ja_inode_flag ***node_flag_ptr, uint8_t n) { @@ -307,6 +308,8 @@ struct cds_ja_inode_flag *ja_linear_node_get_nth(const struct cds_ja_type *type, ptr = rcu_dereference(pointers[i]); if (caa_unlikely(child_node_flag_ptr) && ptr) *child_node_flag_ptr = &pointers[i]; + if (caa_unlikely(child_node_flag_v) && ptr) + *child_node_flag_v = ptr; if (caa_unlikely(node_flag_ptr)) *node_flag_ptr = &pointers[i]; return ptr; @@ -335,6 +338,7 @@ static struct cds_ja_inode_flag *ja_pool_node_get_nth(const struct cds_ja_type *type, struct cds_ja_inode *node, struct cds_ja_inode_flag ***child_node_flag_ptr, + struct cds_ja_inode_flag **child_node_flag_v, struct cds_ja_inode_flag ***node_flag_ptr, uint8_t n) { @@ -348,7 +352,7 @@ struct cds_ja_inode_flag *ja_pool_node_get_nth(const struct cds_ja_type *type, linear = (struct cds_ja_inode *) &node->u.data[((unsigned long) n >> (CHAR_BIT - type->nr_pool_order)) << type->pool_size_order]; return ja_linear_node_get_nth(type, linear, child_node_flag_ptr, - node_flag_ptr, n); + child_node_flag_v, node_flag_ptr, n); } static @@ -365,20 +369,25 @@ static struct cds_ja_inode_flag *ja_pigeon_node_get_nth(const struct cds_ja_type *type, struct cds_ja_inode *node, struct cds_ja_inode_flag ***child_node_flag_ptr, + struct cds_ja_inode_flag **child_node_flag_v, struct cds_ja_inode_flag ***node_flag_ptr, uint8_t n) { struct cds_ja_inode_flag **child_node_flag; + struct cds_ja_inode_flag *child_node_flag_read; assert(type->type_class == RCU_JA_PIGEON); child_node_flag = &((struct cds_ja_inode_flag **) node->u.data)[n]; + child_node_flag_read = rcu_dereference(*child_node_flag); dbg_printf("ja_pigeon_node_get_nth child_node_flag_ptr %p\n", child_node_flag); - if (caa_unlikely(child_node_flag_ptr) && *child_node_flag) + if (caa_unlikely(child_node_flag_ptr) && child_node_flag_read) *child_node_flag_ptr = child_node_flag; + if (caa_unlikely(child_node_flag_v) && child_node_flag_read) + *child_node_flag_v = child_node_flag_read; if (caa_unlikely(node_flag_ptr)) *node_flag_ptr = child_node_flag; - return rcu_dereference(*child_node_flag); + return child_node_flag_read; } static @@ -386,7 +395,7 @@ struct cds_ja_inode_flag *ja_pigeon_node_get_ith_pos(const struct cds_ja_type *t struct cds_ja_inode *node, uint8_t i) { - return ja_pigeon_node_get_nth(type, node, NULL, NULL, i); + return ja_pigeon_node_get_nth(type, node, NULL, NULL, NULL, i); } /* @@ -394,8 +403,9 @@ struct cds_ja_inode_flag *ja_pigeon_node_get_ith_pos(const struct cds_ja_type *t * node_flag is already rcu_dereference'd. */ static -struct cds_ja_inode_flag * ja_node_get_nth(struct cds_ja_inode_flag *node_flag, +struct cds_ja_inode_flag *ja_node_get_nth(struct cds_ja_inode_flag *node_flag, struct cds_ja_inode_flag ***child_node_flag_ptr, + struct cds_ja_inode_flag **child_node_flag, struct cds_ja_inode_flag ***node_flag_ptr, uint8_t n) { @@ -411,13 +421,16 @@ struct cds_ja_inode_flag * ja_node_get_nth(struct cds_ja_inode_flag *node_flag, switch (type->type_class) { case RCU_JA_LINEAR: return ja_linear_node_get_nth(type, node, - child_node_flag_ptr, node_flag_ptr, n); + child_node_flag_ptr, child_node_flag, + node_flag_ptr, n); case RCU_JA_POOL: return ja_pool_node_get_nth(type, node, - child_node_flag_ptr, node_flag_ptr, n); + child_node_flag_ptr, child_node_flag, + node_flag_ptr, n); case RCU_JA_PIGEON: return ja_pigeon_node_get_nth(type, node, - child_node_flag_ptr, node_flag_ptr, n); + child_node_flag_ptr, child_node_flag, + node_flag_ptr, n); default: assert(0); return (void *) -1UL; @@ -950,7 +963,7 @@ struct cds_hlist_head cds_ja_lookup(struct cds_ja *ja, uint64_t key) uint8_t iter_key; iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (tree_depth - i - 1))); - node_flag = ja_node_get_nth(node_flag, NULL, NULL, + node_flag = ja_node_get_nth(node_flag, NULL, NULL, NULL, iter_key); dbg_printf("cds_ja_lookup iter key lookup %u finds node_flag %p\n", (unsigned int) iter_key, node_flag); @@ -978,6 +991,7 @@ struct cds_hlist_head cds_ja_lookup(struct cds_ja *ja, uint64_t key) static int ja_attach_node(struct cds_ja *ja, struct cds_ja_inode_flag **attach_node_flag_ptr, + struct cds_ja_inode_flag *attach_node_flag, struct cds_ja_inode_flag **node_flag_ptr, struct cds_ja_inode_flag *node_flag, struct cds_ja_inode_flag *parent_node_flag, @@ -1013,8 +1027,7 @@ int ja_attach_node(struct cds_ja *ja, } } - if (node_flag_ptr && ja_node_ptr(*node_flag_ptr) != - ja_node_ptr(parent_node_flag)) { + if (node_flag_ptr && ja_node_ptr(*node_flag_ptr)) { /* * Target node has been updated between RCU lookup and * lock acquisition. We need to re-try lookup and @@ -1025,7 +1038,7 @@ int ja_attach_node(struct cds_ja *ja, } if (attach_node_flag_ptr && ja_node_ptr(*attach_node_flag_ptr) != - ja_node_ptr(parent_node_flag)) { + ja_node_ptr(attach_node_flag)) { /* * Target node has been updated between RCU lookup and * lock acquisition. We need to re-try lookup and @@ -1146,7 +1159,8 @@ int cds_ja_add(struct cds_ja *ja, uint64_t key, **node_flag_ptr; struct cds_ja_inode_flag *node_flag, *parent_node_flag, - *parent2_node_flag; + *parent2_node_flag, + *attach_node_flag; int ret; if (caa_unlikely(key > ja->key_max)) { @@ -1161,6 +1175,7 @@ retry: parent_node_flag = (struct cds_ja_inode_flag *) &ja->root; /* Use root ptr address as key for mutex */ attach_node_flag_ptr = &ja->root; + attach_node_flag = rcu_dereference(ja->root); node_flag_ptr = &ja->root; node_flag = rcu_dereference(ja->root); @@ -1172,6 +1187,7 @@ retry: attach_node_flag_ptr, node_flag_ptr, node_flag); if (!ja_node_ptr(node_flag)) { ret = ja_attach_node(ja, attach_node_flag_ptr, + attach_node_flag, node_flag_ptr, parent_node_flag, parent2_node_flag, @@ -1186,6 +1202,7 @@ retry: parent_node_flag = node_flag; node_flag = ja_node_get_nth(node_flag, &attach_node_flag_ptr, + &attach_node_flag, &node_flag_ptr, iter_key); dbg_printf("cds_ja_add iter key lookup %u finds node_flag %p attach_node_flag_ptr %p node_flag_ptr %p\n", @@ -1202,6 +1219,7 @@ retry: dbg_printf("cds_ja_add attach_node_flag_ptr %p node_flag_ptr %p node_flag %p\n", attach_node_flag_ptr, node_flag_ptr, node_flag); ret = ja_attach_node(ja, attach_node_flag_ptr, + attach_node_flag, node_flag_ptr, parent_node_flag, parent2_node_flag, key, i, new_node); } else { @@ -1242,7 +1260,7 @@ int ja_detach_node(struct cds_ja *ja, struct cds_ja_inode_flag **node_flag_ptr = NULL, *parent_node_flag = NULL, **parent_node_flag_ptr = NULL; - struct cds_ja_inode_flag *iter_node_flag, *node_flag = NULL; + struct cds_ja_inode_flag *iter_node_flag; int ret, i, nr_shadow = 0, nr_clear = 0, nr_branch = 0; uint8_t n = 0; @@ -1264,8 +1282,20 @@ int ja_detach_node(struct cds_ja *ja, ret = -EAGAIN; goto end; } - assert(shadow_node->nr_child > 0); shadow_nodes[nr_shadow++] = shadow_node; + + /* + * Check if node has been removed between RCU + * lookup and lock acquisition. + */ + assert(snapshot_ptr[i + 1]); + if (ja_node_ptr(*snapshot_ptr[i + 1]) + != ja_node_ptr(snapshot[i + 1])) { + ret = -ENOENT; + goto end; + } + + assert(shadow_node->nr_child > 0); if (shadow_node->nr_child == 1 && i > 1) nr_clear++; nr_branch++; @@ -1278,32 +1308,22 @@ int ja_detach_node(struct cds_ja *ja, goto end; } shadow_nodes[nr_shadow++] = shadow_node; - node_flag_ptr = snapshot_ptr[i + 1]; - node_flag = snapshot[i + 1]; + /* * Check if node has been removed between RCU * lookup and lock acquisition. */ - assert(node_flag_ptr); - if (ja_node_ptr(*node_flag_ptr) - != ja_node_ptr(node_flag)) { + assert(snapshot_ptr[i]); + if (ja_node_ptr(*snapshot_ptr[i]) + != ja_node_ptr(snapshot[i])) { ret = -ENOENT; goto end; } + node_flag_ptr = snapshot_ptr[i + 1]; n = snapshot_n[i + 1]; parent_node_flag_ptr = snapshot_ptr[i]; parent_node_flag = snapshot[i]; - /* - * Check if node has been removed between RCU - * lookup and lock acquisition. - */ - assert(parent_node_flag_ptr); - if (ja_node_ptr(*parent_node_flag_ptr) - != ja_node_ptr(parent_node_flag)) { - ret = -ENOENT; - goto end; - } if (i > 1) { /* @@ -1317,7 +1337,19 @@ int ja_detach_node(struct cds_ja *ja, goto end; } shadow_nodes[nr_shadow++] = shadow_node; + + /* + * Check if node has been removed between RCU + * lookup and lock acquisition. + */ + assert(snapshot_ptr[i - 1]); + if (ja_node_ptr(*snapshot_ptr[i - 1]) + != ja_node_ptr(snapshot[i - 1])) { + ret = -ENOENT; + goto end; + } } + break; } } @@ -1326,8 +1358,8 @@ int ja_detach_node(struct cds_ja *ja, * At this point, we want to delete all nodes that are about to * be removed from shadow_nodes (except the last one, which is * either the root or the parent of the upmost node with 1 - * child). OK to as to free lock here, because RCU read lock is - * held, and free only performed in call_rcu. + * child). OK to free lock here, because RCU read lock is held, + * and free only performed in call_rcu. */ for (i = 0; i < nr_clear; i++) { @@ -1451,13 +1483,13 @@ retry: snapshot[nr_snapshot++] = node_flag; node_flag = ja_node_get_nth(node_flag, &prev_node_flag_ptr, + NULL, &node_flag_ptr, iter_key); dbg_printf("cds_ja_del iter key lookup %u finds node_flag %p, prev_node_flag_ptr %p\n", (unsigned int) iter_key, node_flag, prev_node_flag_ptr); } - /* * We reached bottom of tree, try to find the node we are trying * to remove. Fail if we cannot find it.