Return-path: Received: from mail-pz0-f42.google.com ([209.85.210.42]:64569 "EHLO mail-pz0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754679Ab1H2Sgi convert rfc822-to-8bit (ORCPT ); Mon, 29 Aug 2011 14:36:38 -0400 Received: by pzk37 with SMTP id 37so8875612pzk.1 for ; Mon, 29 Aug 2011 11:36:38 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1314625745.8959.9.camel@jlt3.sipsolutions.net> References: <1314236452-7226-1-git-send-email-thomas@cozybit.com> <1314404294-4233-1-git-send-email-javier@cozybit.com> <1314404294-4233-7-git-send-email-javier@cozybit.com> <1314625745.8959.9.camel@jlt3.sipsolutions.net> From: Javier Cardona Date: Mon, 29 Aug 2011 11:36:18 -0700 Message-ID: (sfid-20110829_203642_201926_64504E8C) Subject: Re: [PATCH v2 6/8] mac80211: Consolidate {mesh,mpp}_path_flush into one function To: Johannes Berg Cc: "John W. Linville" , Thomas Pedersen , devel@lists.open80211s.org, linux-wireless@vger.kernel.org, jlopex@gmail.com Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Mon, Aug 29, 2011 at 6:49 AM, Johannes Berg wrote: > On Fri, 2011-08-26 at 17:18 -0700, Javier Cardona wrote: >> Signed-off-by: Javier Cardona >> >> --- >> v2: - Fix extra space (checkpatch) >> ? ? - Add lockdep check for RCU >> ?net/mac80211/mesh_pathtbl.c | ? 65 +++++++++++++++++------------------------- >> ?1 files changed, 26 insertions(+), 39 deletions(-) >> >> diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c >> index ea9e34a..3c03be9 100644 >> --- a/net/mac80211/mesh_pathtbl.c >> +++ b/net/mac80211/mesh_pathtbl.c >> @@ -790,35 +790,6 @@ void mesh_plink_broken(struct sta_info *sta) >> ? ? ? rcu_read_unlock(); >> ?} >> >> -/** >> - * mesh_path_flush_by_nexthop - Deletes mesh paths if their next hop matches >> - * >> - * @sta - mesh peer to match >> - * >> - * RCU notes: this function is called when a mesh plink transitions from >> - * PLINK_ESTAB to any other state, since PLINK_ESTAB state is the only one that >> - * allows path creation. This will happen before the sta can be freed (because >> - * sta_info_destroy() calls this) so any reader in a rcu read block will be >> - * protected against the plink disappearing. >> - */ >> -void mesh_path_flush_by_nexthop(struct sta_info *sta) >> -{ >> - ? ? struct mesh_table *tbl; >> - ? ? struct mesh_path *mpath; >> - ? ? struct mpath_node *node; >> - ? ? struct hlist_node *p; >> - ? ? int i; >> - >> - ? ? rcu_read_lock(); >> - ? ? tbl = rcu_dereference(mesh_paths); >> - ? ? for_each_mesh_entry(tbl, p, node, i) { >> - ? ? ? ? ? ? mpath = node->mpath; >> - ? ? ? ? ? ? if (rcu_dereference(mpath->next_hop) == sta) >> - ? ? ? ? ? ? ? ? ? ? mesh_path_del(mpath->dst, mpath->sdata); >> - ? ? } >> - ? ? rcu_read_unlock(); >> -} >> - >> ?static void mesh_path_node_reclaim(struct rcu_head *rp) >> ?{ >> ? ? ? struct mpath_node *node = container_of(rp, struct mpath_node, rcu); >> @@ -845,7 +816,18 @@ static void __mesh_path_del(struct mesh_table *tbl, struct mpath_node *node) >> ? ? ? atomic_dec(&tbl->entries); >> ?} >> >> -static void mesh_path_flush(struct ieee80211_sub_if_data *sdata) >> +/** >> + * mesh_path_flush_by_nexthop - Deletes mesh paths if their next hop matches >> + * >> + * @sta - mesh peer to match >> + * >> + * RCU notes: this function is called when a mesh plink transitions from >> + * PLINK_ESTAB to any other state, since PLINK_ESTAB state is the only one that >> + * allows path creation. This will happen before the sta can be freed (because >> + * sta_info_destroy() calls this) so any reader in a rcu read block will be >> + * protected against the plink disappearing. >> + */ >> +void mesh_path_flush_by_nexthop(struct sta_info *sta) >> ?{ >> ? ? ? struct mesh_table *tbl; >> ? ? ? struct mesh_path *mpath; >> @@ -857,7 +839,7 @@ static void mesh_path_flush(struct ieee80211_sub_if_data *sdata) >> ? ? ? tbl = rcu_dereference(mesh_paths); >> ? ? ? for_each_mesh_entry(tbl, p, node, i) { >> ? ? ? ? ? ? ? mpath = node->mpath; >> - ? ? ? ? ? ? if (mpath->sdata == sdata) { >> + ? ? ? ? ? ? if (rcu_dereference(mpath->next_hop) == sta) { >> ? ? ? ? ? ? ? ? ? ? ? spin_lock_bh(&tbl->hashwlock[i]); >> ? ? ? ? ? ? ? ? ? ? ? __mesh_path_del(tbl, node); >> ? ? ? ? ? ? ? ? ? ? ? spin_unlock_bh(&tbl->hashwlock[i]); >> @@ -866,24 +848,23 @@ static void mesh_path_flush(struct ieee80211_sub_if_data *sdata) >> ? ? ? rcu_read_unlock(); >> ?} >> >> -static void mpp_path_flush(struct ieee80211_sub_if_data *sdata) >> +static void table_flush_by_iface(struct mesh_table *tbl, >> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?struct ieee80211_sub_if_data *sdata) >> ?{ >> - ? ? struct mesh_table *tbl; >> ? ? ? struct mesh_path *mpath; >> ? ? ? struct mpath_node *node; >> ? ? ? struct hlist_node *p; >> ? ? ? int i; >> >> - ? ? read_lock_bh(&pathtbl_resize_lock); >> - ? ? tbl = rcu_dereference_protected(mpp_paths, >> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? lockdep_is_held(pathtbl_resize_lock)); >> + ? ? WARN_ON(!rcu_read_lock_held()); >> ? ? ? for_each_mesh_entry(tbl, p, node, i) { >> ? ? ? ? ? ? ? mpath = node->mpath; >> + ? ? ? ? ? ? if (mpath->sdata != sdata) >> + ? ? ? ? ? ? ? ? ? ? continue; >> ? ? ? ? ? ? ? spin_lock_bh(&tbl->hashwlock[i]); >> ? ? ? ? ? ? ? __mesh_path_del(tbl, node); >> ? ? ? ? ? ? ? spin_unlock_bh(&tbl->hashwlock[i]); >> ? ? ? } >> - ? ? read_unlock_bh(&pathtbl_resize_lock); >> ?} > > So what protects against the table being grown at the same time? A copy > will be made, but here you'll be iterating the old table -- which won't > crash or anything but is semantically incorrect. You are right. And I believe it actually may crash, given that the nodes we wanted to delete will still exist in the new table. I'll re-spin right away. Thanks!