| Message ID | 1304196854-28141-1-git-send-email-sven@narfation.org |
|---|---|
| State | Superseded, archived |
| Headers | show |
Looks quite good and seems to make sense to avoid the double-locking. Tested it here and together with patch 1/3 fixes the initial issue, too. Just one minor thing: ---- [58518.225154] batman_adv: bat0: The MTU of interface eth1 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1527 would solve the problem. [58518.278111] RTNL: assertion failed at /home/mesh-node/incoming/batman-adv-git-builddir/hard-interface.c (136) [58518.293167] Pid: 6366, comm: bash Not tainted 2.6.38+ #4 [58518.299142] Call Trace: [58518.300953] [<f8cb91f3>] primary_if_select+0x2f/0x9f [batman_adv] [58518.447844] [<f8cb8e9c>] ? rcu_read_unlock+0x1c/0x1e [batman_adv] [58518.452572] [<f8cb9146>] ? primary_if_get_selected+0x6a/0x71 [batman_adv] [58518.455759] [<f8cb92c6>] hardif_activate_interface+0x63/0x91 [batman_adv] [58518.459168] [<f8cb98e4>] hardif_enable_interface+0x1cc/0x21e [batman_adv] [58518.462481] [<f8cb7bca>] store_mesh_iface+0xed/0x113 [batman_adv] [58518.465564] [<f8cb7add>] ? store_aggregated_ogms+0x28/0x28 [batman_adv] [58518.468714] [<c11e1121>] kobj_attr_store+0x1a/0x22 [58518.472277] [<c11481dc>] sysfs_write_file+0xbc/0xe7 [58518.613128] [<c1148120>] ? sysfs_open_file+0x205/0x205 [58518.616400] [<c10ff7a7>] vfs_write+0x84/0xde [58518.660437] [<c10ff89a>] sys_write+0x3b/0x60 [58518.667248] [<c151fd9d>] syscall_call+0x7/0xb [58518.672117] batman_adv: bat0: Interface activated: eth1 ---- So maybe it makes sense to add the assertion in primary_if_select() in patch 3/3 instead? Hmm, and I'm wondering if it might make sense to also document it with a little comment above the struct list_head hardif_list;, like: /* List additions and deletions have to be rtnl_lock()'ed, * list traversals just rcu-locked */ (or is that overdoing it?) On Sat, Apr 30, 2011 at 10:54:14PM +0200, Sven Eckelmann wrote: > hardif_list_lock is unneccessary because we already ensure that no > multiple admin operations can take place through rtnl_lock. > hardif_list_lock only adds additional overhead and complexity. > > Critical functions now check whether they are called with rtnl_lock > using ASSERT_RTNL. > > Signed-off-by: Sven Eckelmann <sven@narfation.org> > --- > Rebased patch on top of "batman-adv: Make bat_priv->primary_if an rcu > protected pointer" > > > hard-interface.c | 21 ++++++--------------- > 1 files changed, 6 insertions(+), 15 deletions(-) > > diff --git a/hard-interface.c b/hard-interface.c > index 6636d2f..7e2f772 100644 > --- a/hard-interface.c > +++ b/hard-interface.c > @@ -31,9 +31,6 @@ > > #include <linux/if_arp.h> > > -/* protect update critical side of hardif_list - but not the content */ > -static DEFINE_SPINLOCK(hardif_list_lock); > - > > static int batman_skb_recv(struct sk_buff *skb, > struct net_device *dev, > @@ -136,7 +133,7 @@ static void primary_if_select(struct bat_priv *bat_priv, > struct hard_iface *curr_hard_iface; > struct batman_packet *batman_packet; > > - spin_lock_bh(&hardif_list_lock); > + ASSERT_RTNL(); > > if (new_hard_iface && !atomic_inc_not_zero(&new_hard_iface->refcount)) > new_hard_iface = NULL; > @@ -148,7 +145,7 @@ static void primary_if_select(struct bat_priv *bat_priv, > hardif_free_ref(curr_hard_iface); > > if (!new_hard_iface) > - goto out; > + return; > > batman_packet = (struct batman_packet *)(new_hard_iface->packet_buff); > batman_packet->flags = PRIMARIES_FIRST_HOP; > @@ -161,9 +158,6 @@ static void primary_if_select(struct bat_priv *bat_priv, > * our new primary interface > */ > atomic_set(&bat_priv->hna_local_changed, 1); > - > -out: > - spin_unlock_bh(&hardif_list_lock); > } > > static bool hardif_is_iface_up(struct hard_iface *hard_iface) > @@ -456,6 +450,8 @@ static struct hard_iface *hardif_add_interface(struct net_device *net_dev) > struct hard_iface *hard_iface; > int ret; > > + ASSERT_RTNL(); > + > ret = is_valid_iface(net_dev); > if (ret != 1) > goto out; > @@ -482,10 +478,7 @@ static struct hard_iface *hardif_add_interface(struct net_device *net_dev) > atomic_set(&hard_iface->refcount, 2); > > check_known_mac_addr(hard_iface->net_dev); > - > - spin_lock(&hardif_list_lock); > list_add_tail_rcu(&hard_iface->list, &hardif_list); > - spin_unlock(&hardif_list_lock); > > return hard_iface; > > @@ -499,6 +492,8 @@ out: > > static void hardif_remove_interface(struct hard_iface *hard_iface) > { > + ASSERT_RTNL(); > + > /* first deactivate interface */ > if (hard_iface->if_status != IF_NOT_IN_USE) > hardif_disable_interface(hard_iface); > @@ -516,13 +511,11 @@ void hardif_remove_interfaces(void) > struct hard_iface *hard_iface, *hard_iface_tmp; > > rtnl_lock(); > - spin_lock(&hardif_list_lock); > list_for_each_entry_safe(hard_iface, hard_iface_tmp, > &hardif_list, list) { > list_del_rcu(&hard_iface->list); > hardif_remove_interface(hard_iface); > } > - spin_unlock(&hardif_list_lock); > rtnl_unlock(); > } > > @@ -549,9 +542,7 @@ static int hard_if_event(struct notifier_block *this, > hardif_deactivate_interface(hard_iface); > break; > case NETDEV_UNREGISTER: > - spin_lock(&hardif_list_lock); > list_del_rcu(&hard_iface->list); > - spin_unlock(&hardif_list_lock); > > hardif_remove_interface(hard_iface); > break; > -- > 1.7.4.4 >
Linus Lüssing wrote: > Looks quite good and seems to make sense to avoid the > double-locking. Tested it here and together with patch 1/3 fixes > the initial issue, too. > > Just one minor thing: > ---- > [58518.225154] batman_adv: bat0: The MTU of interface eth1 is too > small (1500) to handle the transport of batman-adv packets. > Packets going over this interface will be fragmented on layer2 > which could impact the performance. Setting the MTU to 1527 would > solve the problem. > [58518.278111] RTNL: assertion failed at > /home/mesh-node/incoming/batman-adv-git-builddir/hard-interface.c > (136) > [58518.293167] Pid: 6366, comm: bash Not tainted 2.6.38+ #4 > [58518.299142] Call Trace: > [58518.300953] [<f8cb91f3>] primary_if_select+0x2f/0x9f > [batman_adv] > [58518.447844] [<f8cb8e9c>] ? rcu_read_unlock+0x1c/0x1e > [batman_adv] > [58518.452572] [<f8cb9146>] ? primary_if_get_selected+0x6a/0x71 > [batman_adv] > [58518.455759] [<f8cb92c6>] hardif_activate_interface+0x63/0x91 > [batman_adv] > [58518.459168] [<f8cb98e4>] hardif_enable_interface+0x1cc/0x21e > [batman_adv] > [58518.462481] [<f8cb7bca>] store_mesh_iface+0xed/0x113 > [batman_adv] > [58518.465564] [<f8cb7add>] ? store_aggregated_ogms+0x28/0x28 > [batman_adv] > [58518.468714] [<c11e1121>] kobj_attr_store+0x1a/0x22 > [58518.472277] [<c11481dc>] sysfs_write_file+0xbc/0xe7 > [58518.613128] [<c1148120>] ? sysfs_open_file+0x205/0x205 > [58518.616400] [<c10ff7a7>] vfs_write+0x84/0xde > [58518.660437] [<c10ff89a>] sys_write+0x3b/0x60 > [58518.667248] [<c151fd9d>] syscall_call+0x7/0xb > [58518.672117] batman_adv: bat0: Interface activated: eth1 > ---- > > So maybe it makes sense to add the assertion in > primary_if_select() in patch 3/3 instead? No, the problem is that I changed the patch after I noticed that it wasn't made for the current master - and only tested after all patches were applied. I would like to add rtnl_lock/rtnl_unlock around primary_if_get_selected() instead. > Hmm, and I'm wondering if it might make sense to also document it > with a little comment above the struct list_head hardif_list;, > like: > /* List additions and deletions have to be rtnl_lock()'ed, > * list traversals just rcu-locked */ > (or is that overdoing it?) Ok, will steal this comment from your mail - ok, change it slightly to present it as my own work. Kind regards, Sven
diff --git a/hard-interface.c b/hard-interface.c index 6636d2f..7e2f772 100644 --- a/hard-interface.c +++ b/hard-interface.c @@ -31,9 +31,6 @@ #include <linux/if_arp.h> -/* protect update critical side of hardif_list - but not the content */ -static DEFINE_SPINLOCK(hardif_list_lock); - static int batman_skb_recv(struct sk_buff *skb, struct net_device *dev, @@ -136,7 +133,7 @@ static void primary_if_select(struct bat_priv *bat_priv, struct hard_iface *curr_hard_iface; struct batman_packet *batman_packet; - spin_lock_bh(&hardif_list_lock); + ASSERT_RTNL(); if (new_hard_iface && !atomic_inc_not_zero(&new_hard_iface->refcount)) new_hard_iface = NULL; @@ -148,7 +145,7 @@ static void primary_if_select(struct bat_priv *bat_priv, hardif_free_ref(curr_hard_iface); if (!new_hard_iface) - goto out; + return; batman_packet = (struct batman_packet *)(new_hard_iface->packet_buff); batman_packet->flags = PRIMARIES_FIRST_HOP; @@ -161,9 +158,6 @@ static void primary_if_select(struct bat_priv *bat_priv, * our new primary interface */ atomic_set(&bat_priv->hna_local_changed, 1); - -out: - spin_unlock_bh(&hardif_list_lock); } static bool hardif_is_iface_up(struct hard_iface *hard_iface) @@ -456,6 +450,8 @@ static struct hard_iface *hardif_add_interface(struct net_device *net_dev) struct hard_iface *hard_iface; int ret; + ASSERT_RTNL(); + ret = is_valid_iface(net_dev); if (ret != 1) goto out; @@ -482,10 +478,7 @@ static struct hard_iface *hardif_add_interface(struct net_device *net_dev) atomic_set(&hard_iface->refcount, 2); check_known_mac_addr(hard_iface->net_dev); - - spin_lock(&hardif_list_lock); list_add_tail_rcu(&hard_iface->list, &hardif_list); - spin_unlock(&hardif_list_lock); return hard_iface; @@ -499,6 +492,8 @@ out: static void hardif_remove_interface(struct hard_iface *hard_iface) { + ASSERT_RTNL(); + /* first deactivate interface */ if (hard_iface->if_status != IF_NOT_IN_USE) hardif_disable_interface(hard_iface); @@ -516,13 +511,11 @@ void hardif_remove_interfaces(void) struct hard_iface *hard_iface, *hard_iface_tmp; rtnl_lock(); - spin_lock(&hardif_list_lock); list_for_each_entry_safe(hard_iface, hard_iface_tmp, &hardif_list, list) { list_del_rcu(&hard_iface->list); hardif_remove_interface(hard_iface); } - spin_unlock(&hardif_list_lock); rtnl_unlock(); } @@ -549,9 +542,7 @@ static int hard_if_event(struct notifier_block *this, hardif_deactivate_interface(hard_iface); break; case NETDEV_UNREGISTER: - spin_lock(&hardif_list_lock); list_del_rcu(&hard_iface->list); - spin_unlock(&hardif_list_lock); hardif_remove_interface(hard_iface); break;
hardif_list_lock is unneccessary because we already ensure that no multiple admin operations can take place through rtnl_lock. hardif_list_lock only adds additional overhead and complexity. Critical functions now check whether they are called with rtnl_lock using ASSERT_RTNL. Signed-off-by: Sven Eckelmann <sven@narfation.org> --- Rebased patch on top of "batman-adv: Make bat_priv->primary_if an rcu protected pointer" hard-interface.c | 21 ++++++--------------- 1 files changed, 6 insertions(+), 15 deletions(-)