Bug 28052

Summary: [BUG] 2.6.38-rc2: Circular Locking Dependency
Product: Networking Reporter: Maciej Rutecki (maciej.rutecki)
Component: OtherAssignee: Arnaldo Carvalho de Melo (acme)
Status: CLOSED CODE_FIX    
Severity: normal CC: Knut_Petersen, maciej.rutecki, rjw
Priority: P1    
Hardware: All   
OS: Linux   
Kernel Version: 2.6.38-rc2 Subsystem:
Regression: Yes Bisected commit-id:
Bug Depends on:    
Bug Blocks: 27352    

Description Maciej Rutecki 2011-02-01 20:58:06 UTC 
Subject    : [BUG] 2.6.38-rc2: Circular Locking Dependency
Submitter  : Knut Petersen <Knut_Petersen@t-online.de>
Date       : 2011-01-24 9:25
Message-ID : 4D3D45A3.7040809@t-online.de
References : http://marc.info/?l=linux-kernel&m=129586118515443&w=2

This entry is being used for tracking a regression from 2.6.37. Please don't
close it until the problem is fixed in the mainline.
Comment 1 Rafael J. Wysocki 2011-02-13 23:40:18 UTC 
On Sunday, February 13, 2011, David Miller wrote:
> From: "Rafael J. Wysocki" <rjw@sisk.pl>
> Date: Sun, 13 Feb 2011 00:05:18 +0100 (CET)
> 
> > Bug-Entry   : http://bugzilla.kernel.org/show_bug.cgi?id=28052
> > Subject             : [BUG] 2.6.38-rc2: Circular Locking Dependency
> > Submitter   : Knut Petersen <Knut_Petersen@t-online.de>
> > Date                : 2011-01-24 9:25 (20 days old)
> > Message-ID  : <4D3D45A3.7040809@t-online.de>
> > References  : http://marc.info/?l=linux-kernel&m=129586118515443&w=2
> 
> Fixed by:
> 
> commit 8d3bdbd55a7e2a3f2c148a4830aa26dd682b21c4
> Author: David S. Miller <davem@davemloft.net>
> Date:   Tue Feb 8 15:02:50 2011 -0800
> 
>     net: Fix lockdep regression caused by initializing netdev queues too
>     early.
>     
>     In commit aa9421041128abb4d269ee1dc502ff65fb3b7d69 ("net: init ingress
>     queue") we moved the allocation and lock initialization of the queues
>     into alloc_netdev_mq() since register_netdevice() is way too late.
>     
>     The problem is that dev->type is not setup until the setup()
>     callback is invoked by alloc_netdev_mq(), and the dev->type is
>     what determines the lockdep class to use for the locks in the
>     queues.
>     
>     Fix this by doing the queue allocation after the setup() callback
>     runs.
>     
>     This is safe because the setup() callback is not allowed to make any
>     state changes that need to be undone on error (memory allocations,
>     etc.).  It may, however, make state changes that are undone by
>     free_netdev() (such as netif_napi_add(), which is done by the
>     ipoib driver's setup routine).
>     
>     The previous code also leaked a reference to the &init_net namespace
>     object on RX/TX queue allocation failures.
>     
>     Signed-off-by: David S. Miller <davem@davemloft.net>