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Message-ID: <20080615194415.GB2824@yamamaya.is-a-geek.org>
Date: Sun, 15 Jun 2008 21:44:15 +0200
From: Tobias Diedrich <ranma+kernel@...edrich.de>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
Ayaz Abdulla <aabdulla@...dia.com>
Subject: [PATCH] Re: forcedeth: lockdep warning on ethtool -s
Andrew Morton wrote:
> On Sun, 1 Jun 2008 10:37:01 +0200 Tobias Diedrich <ranma+kernel@...edrich.de> wrote:
>
> > Hi,
> >
> > 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
> >
> >
> > I think 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.
>
> Could you please try that and if it works, send the patch?
Here you go, with this patch applied I get no warning:
Signed-Off-By: Tobias Diedrich <ranma+kernel@...edrich.de>
Index: linux-2.6.26-rc4.forcedwol/drivers/net/forcedeth.c
===================================================================
--- linux-2.6.26-rc4.forcedwol.orig/drivers/net/forcedeth.c 2008-06-15 20:45:32.000000000 +0200
+++ linux-2.6.26-rc4.forcedwol/drivers/net/forcedeth.c 2008-06-15 20:55:27.000000000 +0200
@@ -4198,12 +4198,23 @@
netif_carrier_off(dev);
if (netif_running(dev)) {
+ unsigned long flags;
+
nv_disable_irq(dev);
netif_tx_lock_bh(dev);
- spin_lock(&np->lock);
+ /* with plain spinlock lockdep complains */
+ spin_lock_irqsave(&np->lock, flags);
/* stop engines */
+ /* FIXME:
+ * this can take some time, and interrupts are disabled
+ * due to spin_lock_irqsave, but let's hope no daemon
+ * is going to change the settings very often...
+ * Worst case:
+ * NV_RXSTOP_DELAY1MAX + NV_TXSTOP_DELAY1MAX
+ * + some minor delays, which is up to a second approximately
+ */
nv_stop_rxtx(dev);
- spin_unlock(&np->lock);
+ spin_unlock_irqrestore(&np->lock, flags);
netif_tx_unlock_bh(dev);
}
--
Tobias PGP: http://9ac7e0bc.uguu.de
このメールは十割再利用されたビットで作られています。
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