• Tobias Diedrich's avatar
    forcedeth: fix lockdep warning on ethtool -s · 97bff095
    Tobias Diedrich authored
    
    
    After enabling CONFIG_LOCKDEP and CONFIG_PROVE_LOCKING I get the
    following warning when ethtool -s is first called on one of the
    forcedeth ports:
    
    =================================
    [ INFO: inconsistent lock state ]
    2.6.26-rc4 #28
    ---------------------------------
    inconsistent {in-hardirq-W} -> {hardirq-on-W} usage.
    ethtool/1985 [HC0[0]:SC0[1]:HE1:SE0] takes:
     (&np->lock){++..}, at: [<ffffffffa000c5fd>] nv_set_settings+0xc8/0x3de [forcedeth]
    {in-hardirq-W} state was registered at:
      [<ffffffffffffffff>] 0xffffffffffffffff
    irq event stamp: 3606
    hardirqs last  enabled at (3605): [<ffffffff8068106f>] _spin_unlock_irqrestore+0x3f/0x68
    hardirqs last disabled at (3604): [<ffffffff80680d38>] _spin_lock_irqsave+0x13/0x46
    softirqs last  enabled at (3534): [<ffffffff80246ba5>] __do_softirq+0xbc/0xc5
    softirqs last disabled at (3606): [<ffffffff80680b33>] _spin_lock_bh+0x11/0x41
    
    other info that might help us debug this:
    2 locks held by ethtool/1985:
     #0:  (rtnl_mutex){--..}, at: [<ffffffff80596072>] rtnl_lock+0x12/0x14
     #1:  (_xmit_ETHER){-+..}, at: [<ffffffffa000c5e8>] nv_set_settings+0xb3/0x3de [forcedeth]
    stack backtrace:
    Pid: 1985, comm: ethtool Not tainted 2.6.26-rc4 #28
    Call Trace:
     [<ffffffff8025f190>] print_usage_bug+0x162/0x173
     [<ffffffff8025fa8b>] mark_lock+0x231/0x41f
     [<ffffffff802607cf>] __lock_acquire+0x4e7/0xcac
     [<ffffffff8025fe64>] ? trace_hardirqs_on+0xf1/0x115
     [<ffffffff80272c3a>] ? disable_irq_nosync+0x6f/0x7b
     [<ffffffff80261375>] lock_acquire+0x55/0x6e
     [<ffffffffa000c5fd>] ? :forcedeth:nv_set_settings+0xc8/0x3de
     [<ffffffff80680b15>] _spin_lock+0x2f/0x3c
     [<ffffffffa000c5fd>] :forcedeth:nv_set_settings+0xc8/0x3de
     [<ffffffff8058f8bb>] dev_ethtool+0x186/0xea3
     [<ffffffff8067f446>] ? mutex_lock_nested+0x243/0x275
     [<ffffffff8025df2b>] ? debug_mutex_free_waiter+0x46/0x4a
     [<ffffffff8067f469>] ? mutex_lock_nested+0x266/0x275
     [<ffffffff8058e1ce>] dev_ioctl+0x4eb/0x600
     [<ffffffff8068106f>] ? _spin_unlock_irqrestore+0x3f/0x68
     [<ffffffff80580f91>] sock_ioctl+0x1f5/0x202
     [<ffffffff802a322e>] vfs_ioctl+0x2a/0x77
     [<ffffffff802a34d6>] do_vfs_ioctl+0x25b/0x270
     [<ffffffff806807b6>] ? trace_hardirqs_on_thunk+0x35/0x3a
     [<ffffffff802a352d>] sys_ioctl+0x42/0x65
     [<ffffffff8021fffb>] system_call_after_swapgs+0x7b/0x80
    
    This is caused by the following snippet in nv_set_settings:
    
    	netif_carrier_off(dev);
    	if (netif_running(dev)) {
    		nv_disable_irq(dev);
    		netif_tx_lock_bh(dev);
    		spin_lock(&np->lock);
    		/* stop engines */
    		nv_stop_rxtx(dev);
    		spin_unlock(&np->lock);
    		netif_tx_unlock_bh(dev);
    	}
    
    Because of nv_disable_irq this is probably not really a problem
    though (I guess) and replacing the spin_lock with spin_lock_irqsave
    could keep interrupts disabled for a longer period of time because
    of delays in nv_stop_rx and nv_stop_tx.
    Signed-off-by: default avatarTobias Diedrich <ranma+kernel@tdiedrich.de>
    Cc: Ayaz Abdulla <aabdulla@nvidia.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarJeff Garzik <jgarzik@redhat.com>
    97bff095