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batman-adv: Avoid RCU list-traversal in spinlock

Message ID 20200216180025.14271-1-sven@narfation.org
State Accepted, archived
Delegated to: Simon Wunderlich
Headers show
Series batman-adv: Avoid RCU list-traversal in spinlock | expand

Commit Message

Sven Eckelmann Feb. 16, 2020, 6 p.m. UTC
The new CONFIG_PROVE_RCU_LIST requires a condition statement in
(h)list_for_each_entry_rcu when the code might be executed in a non RCU
non-reader section with the writer lock. Otherwise lockdep might cause a
false positive warning like

  WARNING: suspicious RCU usage
  translation-table.c:940 RCU-list traversed in non-reader section!!

batman-adv is (mostly) following the examples from the RCU documenation and
is using the normal list-traversal primitives instead of the RCU
list-traversal primitives when the writer (spin)lock is held.

The remaining users of RCU list-traversal primitives with writer spinlock
have to be converted to the same style as the rest of the code.

Reported-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
 net/batman-adv/translation-table.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
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diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 85293283..2d52356a 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -862,7 +862,7 @@  batadv_tt_prepare_tvlv_global_data(struct batadv_orig_node *orig_node,
 	u8 *tt_change_ptr;
-	hlist_for_each_entry_rcu(vlan, &orig_node->vlan_list, list) {
+	hlist_for_each_entry(vlan, &orig_node->vlan_list, list) {
 		num_entries += atomic_read(&vlan->tt.num_entries);
@@ -888,7 +888,7 @@  batadv_tt_prepare_tvlv_global_data(struct batadv_orig_node *orig_node,
 	(*tt_data)->num_vlan = htons(num_vlan);
 	tt_vlan = (struct batadv_tvlv_tt_vlan_data *)(*tt_data + 1);
-	hlist_for_each_entry_rcu(vlan, &orig_node->vlan_list, list) {
+	hlist_for_each_entry(vlan, &orig_node->vlan_list, list) {
 		tt_vlan->vid = htons(vlan->vid);
 		tt_vlan->crc = htonl(vlan->tt.crc);
@@ -937,7 +937,7 @@  batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 	int change_offset;
-	hlist_for_each_entry_rcu(vlan, &bat_priv->softif_vlan_list, list) {
+	hlist_for_each_entry(vlan, &bat_priv->softif_vlan_list, list) {
 		vlan_entries = atomic_read(&vlan->tt.num_entries);
 		if (vlan_entries < 1)