[net-next,v2] netpoll: fix a rtnl lock assertion failure

Submitted by Amerigo Wang on Jan. 14, 2013, 10:24 a.m.

Details

Message ID 1358159054-21951-1-git-send-email-amwang@redhat.com
State Superseded
Delegated to: David Miller
Headers show

Commit Message

Amerigo Wang Jan. 14, 2013, 10:24 a.m.
From: Cong Wang <amwang@redhat.com>

This patch fixes the following warning:

[   72.013864] RTNL: assertion failed at net/core/dev.c (4955)
[   72.017758] Pid: 668, comm: netpoll-prep-v6 Not tainted 3.8.0-rc1+ #474
[   72.019582] Call Trace:
[   72.020295]  [<ffffffff8176653d>] netdev_master_upper_dev_get+0x35/0x58
[   72.022545]  [<ffffffff81784edd>] netpoll_setup+0x61/0x340
[   72.024846]  [<ffffffff815d837e>] store_enabled+0x82/0xc3
[   72.027466]  [<ffffffff815d7e51>] netconsole_target_attr_store+0x35/0x37
[   72.029348]  [<ffffffff811c3479>] configfs_write_file+0xe2/0x10c
[   72.030959]  [<ffffffff8115d239>] vfs_write+0xaf/0xf6
[   72.032359]  [<ffffffff81978a05>] ? sysret_check+0x22/0x5d
[   72.033824]  [<ffffffff8115d453>] sys_write+0x5c/0x84
[   72.035328]  [<ffffffff819789d9>] system_call_fastpath+0x16/0x1b

Just hold RCU read lock and call netdev_master_upper_dev_get_rcu(),
as suggested by Jiri.

Cc: Jiri Pirko <jiri@resnulli.us>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>

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Comments

Jiri Pirko Jan. 14, 2013, 10:32 a.m.
Mon, Jan 14, 2013 at 11:24:14AM CET, amwang@redhat.com wrote:
>From: Cong Wang <amwang@redhat.com>
>
>This patch fixes the following warning:
>
>[   72.013864] RTNL: assertion failed at net/core/dev.c (4955)
>[   72.017758] Pid: 668, comm: netpoll-prep-v6 Not tainted 3.8.0-rc1+ #474
>[   72.019582] Call Trace:
>[   72.020295]  [<ffffffff8176653d>] netdev_master_upper_dev_get+0x35/0x58
>[   72.022545]  [<ffffffff81784edd>] netpoll_setup+0x61/0x340
>[   72.024846]  [<ffffffff815d837e>] store_enabled+0x82/0xc3
>[   72.027466]  [<ffffffff815d7e51>] netconsole_target_attr_store+0x35/0x37
>[   72.029348]  [<ffffffff811c3479>] configfs_write_file+0xe2/0x10c
>[   72.030959]  [<ffffffff8115d239>] vfs_write+0xaf/0xf6
>[   72.032359]  [<ffffffff81978a05>] ? sysret_check+0x22/0x5d
>[   72.033824]  [<ffffffff8115d453>] sys_write+0x5c/0x84
>[   72.035328]  [<ffffffff819789d9>] system_call_fastpath+0x16/0x1b
>
>Just hold RCU read lock and call netdev_master_upper_dev_get_rcu(),
>as suggested by Jiri.
>
>Cc: Jiri Pirko <jiri@resnulli.us>
>Cc: David S. Miller <davem@davemloft.net>
>Signed-off-by: Cong Wang <amwang@redhat.com>
>
>---
>diff --git a/net/core/netpoll.c b/net/core/netpoll.c
>index 9f05067..6d56b57 100644
>--- a/net/core/netpoll.c
>+++ b/net/core/netpoll.c
>@@ -1055,11 +1055,15 @@ int netpoll_setup(struct netpoll *np)
> 		return -ENODEV;
> 	}
> 
>-	if (netdev_master_upper_dev_get(ndev)) {
>+	rcu_read_lock();
>+	/* We permit devices with VLAN attached to */

I think that this comment might be misleading. Master upper is not set
not only for VLAN but for macvlan (and in future possibly for others) as well.	

Apart from this, the patch looks good to me.

>+	if (netdev_master_upper_dev_get_rcu(ndev)) {
>+		rcu_read_unlock();
> 		np_err(np, "%s is a slave device, aborting\n", np->dev_name);
> 		err = -EBUSY;
> 		goto put;
> 	}
>+	rcu_read_unlock();
> 
> 	if (!netif_running(ndev)) {
> 		unsigned long atmost, atleast;
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Amerigo Wang Jan. 14, 2013, 10:42 a.m.
On Mon, 2013-01-14 at 11:32 +0100, Jiri Pirko wrote:
> Mon, Jan 14, 2013 at 11:24:14AM CET, amwang@redhat.com wrote:
> >From: Cong Wang <amwang@redhat.com>
> >
> >This patch fixes the following warning:
> >
> >[   72.013864] RTNL: assertion failed at net/core/dev.c (4955)
> >[   72.017758] Pid: 668, comm: netpoll-prep-v6 Not tainted 3.8.0-rc1+ #474
> >[   72.019582] Call Trace:
> >[   72.020295]  [<ffffffff8176653d>] netdev_master_upper_dev_get+0x35/0x58
> >[   72.022545]  [<ffffffff81784edd>] netpoll_setup+0x61/0x340
> >[   72.024846]  [<ffffffff815d837e>] store_enabled+0x82/0xc3
> >[   72.027466]  [<ffffffff815d7e51>] netconsole_target_attr_store+0x35/0x37
> >[   72.029348]  [<ffffffff811c3479>] configfs_write_file+0xe2/0x10c
> >[   72.030959]  [<ffffffff8115d239>] vfs_write+0xaf/0xf6
> >[   72.032359]  [<ffffffff81978a05>] ? sysret_check+0x22/0x5d
> >[   72.033824]  [<ffffffff8115d453>] sys_write+0x5c/0x84
> >[   72.035328]  [<ffffffff819789d9>] system_call_fastpath+0x16/0x1b
> >
> >Just hold RCU read lock and call netdev_master_upper_dev_get_rcu(),
> >as suggested by Jiri.
> >
> >Cc: Jiri Pirko <jiri@resnulli.us>
> >Cc: David S. Miller <davem@davemloft.net>
> >Signed-off-by: Cong Wang <amwang@redhat.com>
> >
> >---
> >diff --git a/net/core/netpoll.c b/net/core/netpoll.c
> >index 9f05067..6d56b57 100644
> >--- a/net/core/netpoll.c
> >+++ b/net/core/netpoll.c
> >@@ -1055,11 +1055,15 @@ int netpoll_setup(struct netpoll *np)
> > 		return -ENODEV;
> > 	}
> > 
> >-	if (netdev_master_upper_dev_get(ndev)) {
> >+	rcu_read_lock();
> >+	/* We permit devices with VLAN attached to */
> 
> I think that this comment might be misleading. Master upper is not set
> not only for VLAN but for macvlan (and in future possibly for others) as well.	
> 

OK, I will remove it.


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Patch hide | download patch | download mbox

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 9f05067..6d56b57 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -1055,11 +1055,15 @@  int netpoll_setup(struct netpoll *np)
 		return -ENODEV;
 	}
 
-	if (netdev_master_upper_dev_get(ndev)) {
+	rcu_read_lock();
+	/* We permit devices with VLAN attached to */
+	if (netdev_master_upper_dev_get_rcu(ndev)) {
+		rcu_read_unlock();
 		np_err(np, "%s is a slave device, aborting\n", np->dev_name);
 		err = -EBUSY;
 		goto put;
 	}
+	rcu_read_unlock();
 
 	if (!netif_running(ndev)) {
 		unsigned long atmost, atleast;