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

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Submitter Amerigo Wang
Date Jan. 14, 2013, 8:55 a.m.
Message ID <1358153708-9099-1-git-send-email-amwang@redhat.com>
Download mbox | patch
Permalink /patch/211733/
State Superseded
Delegated to: David Miller
Headers show

Comments

Amerigo Wang - Jan. 14, 2013, 8:55 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

by holding the rtnl_lock. And as we just want test if the device
has any upper device, so I think netdev_has_any_upper_dev() is enough.

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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Jiri Pirko - Jan. 14, 2013, 9:15 a.m.
Mon, Jan 14, 2013 at 09:55:08AM 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
>
>by holding the rtnl_lock. And as we just want test if the device
>has any upper device, so I think netdev_has_any_upper_dev() is enough.
>
>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..dd28cdd 100644
>--- a/net/core/netpoll.c
>+++ b/net/core/netpoll.c
>@@ -1055,7 +1055,9 @@ int netpoll_setup(struct netpoll *np)
> 		return -ENODEV;
> 	}
> 
>-	if (netdev_master_upper_dev_get(ndev)) {
>+	rtnl_lock();
>+	if (netdev_has_any_upper_dev(ndev)) {

	
This would prevent from using dev with for example vlan dev attached to
it. Is it desirable? I suppose not.

Also I think in this situation, netdev_master_upper_dev_get_rcu() would
be probably better to use. Not sure though.

	
>+		rtnl_unlock();
> 		np_err(np, "%s is a slave device, aborting\n", np->dev_name);
> 		err = -EBUSY;
> 		goto put;
>@@ -1066,7 +1068,6 @@ int netpoll_setup(struct netpoll *np)
> 
> 		np_info(np, "device %s not up yet, forcing it\n", np->dev_name);
> 
>-		rtnl_lock();
> 		err = dev_open(ndev);
> 		rtnl_unlock();
> 
>@@ -1094,7 +1095,8 @@ int netpoll_setup(struct netpoll *np)
> 			np_notice(np, "carrier detect appears untrustworthy, waiting 4 seconds\n");
> 			msleep(4000);
> 		}
>-	}
>+	} else
>+		rtnl_unlock();
> 
> 	if (!np->local_ip.ip) {
> 		if (!np->ipv6) {
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Amerigo Wang - Jan. 14, 2013, 9:58 a.m.
On Mon, 2013-01-14 at 10:15 +0100, Jiri Pirko wrote:
> Mon, Jan 14, 2013 at 09:55:08AM 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
> >
> >by holding the rtnl_lock. And as we just want test if the device
> >has any upper device, so I think netdev_has_any_upper_dev() is enough.
> >
> >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..dd28cdd 100644
> >--- a/net/core/netpoll.c
> >+++ b/net/core/netpoll.c
> >@@ -1055,7 +1055,9 @@ int netpoll_setup(struct netpoll *np)
> > 		return -ENODEV;
> > 	}
> > 
> >-	if (netdev_master_upper_dev_get(ndev)) {
> >+	rtnl_lock();
> >+	if (netdev_has_any_upper_dev(ndev)) {
> 
> 	
> This would prevent from using dev with for example vlan dev attached to
> it. Is it desirable? I suppose not.

No, it should not. I didn't notice netdev_has_any_upper_dev() could
prevent the device under vlan, I will keep
netdev_master_upper_dev_get().

> 
> Also I think in this situation, netdev_master_upper_dev_get_rcu() would
> be probably better to use. Not sure though.
> 

Yes, as we only read it.

Thanks!

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Patch

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 9f05067..dd28cdd 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -1055,7 +1055,9 @@  int netpoll_setup(struct netpoll *np)
 		return -ENODEV;
 	}
 
-	if (netdev_master_upper_dev_get(ndev)) {
+	rtnl_lock();
+	if (netdev_has_any_upper_dev(ndev)) {
+		rtnl_unlock();
 		np_err(np, "%s is a slave device, aborting\n", np->dev_name);
 		err = -EBUSY;
 		goto put;
@@ -1066,7 +1068,6 @@  int netpoll_setup(struct netpoll *np)
 
 		np_info(np, "device %s not up yet, forcing it\n", np->dev_name);
 
-		rtnl_lock();
 		err = dev_open(ndev);
 		rtnl_unlock();
 
@@ -1094,7 +1095,8 @@  int netpoll_setup(struct netpoll *np)
 			np_notice(np, "carrier detect appears untrustworthy, waiting 4 seconds\n");
 			msleep(4000);
 		}
-	}
+	} else
+		rtnl_unlock();
 
 	if (!np->local_ip.ip) {
 		if (!np->ipv6) {