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* lockdep warnings in ipv6
@ 2008-02-24 12:10 Jan Engelhardt
  2008-02-24 13:12 ` Kristof Provost
  2008-02-25  1:16 ` David Miller
  0 siblings, 2 replies; 3+ messages in thread
From: Jan Engelhardt @ 2008-02-24 12:10 UTC (permalink / raw)
  To: netdev; +Cc: Linux Kernel Mailing List

Hi,


when doing IPv6 (ping6, ssh otherhost, etc.), lockdep spews a warning in 
2.6.25-rc2 on the target. CONFIG_..._FRAME_POINTER is off,

CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER=y
# CONFIG_FRAME_POINTER is not set

so I am not sure if the stack trace is worth something, is it?

[  449.168320] =======================================================
[  449.168637] [ INFO: possible circular locking dependency detected ]
[  449.168851] 2.6.25-rc2 #67
[  449.168951] -------------------------------------------------------
[  449.169078] swapper/0 is trying to acquire lock:
[  449.169315]  (&tbl->lock){-+-+}, at: [<c023d5a3>] 
neigh_lookup+0x43/0xb0
[  449.170147] 
[  449.170150] but task is already holding lock:
[  449.170309]  (&n->lock){-+-+}, at: [<c023f975>] 
neigh_timer_handler+0x15/0x2a0
[  449.170512] 
[  449.170514] which lock already depends on the new lock.
[  449.170516] 
[  449.170736] 
[  449.170738] the existing dependency chain (in reverse order) is:
[  449.170926] 
[  449.170927] -> #1 (&n->lock){-+-+}:
[  449.171188]        [<c0132266>] add_lock_to_list+0x46/0xc0
[  449.171509]        [<c0134c48>] __lock_acquire+0xb48/0xf90
[  449.171678]        [<c023dcda>] neigh_periodic_timer+0x7a/0x170
[  449.171849]        [<c01350ef>] lock_acquire+0x5f/0x80
[  449.172007]        [<c023dcda>] neigh_periodic_timer+0x7a/0x170
[  449.172173]        [<c029b239>] _write_lock+0x29/0x40
[  449.172342]        [<c023dcda>] neigh_periodic_timer+0x7a/0x170
[  449.172508]        [<c023dcda>] neigh_periodic_timer+0x7a/0x170
[  449.172670]        [<c011dd5f>] run_timer_softirq+0x15f/0x1c0
[  449.172984]        [<c023dc60>] neigh_periodic_timer+0x0/0x170
[  449.173180]        [<c023dc60>] neigh_periodic_timer+0x0/0x170
[  449.173349]        [<c011a182>] __do_softirq+0x52/0xb0
[  449.173516]        [<c011a225>] do_softirq+0x45/0x50
[  449.173675]        [<c011a665>] irq_exit+0x55/0x70
[  449.173831]        [<c0104e83>] do_IRQ+0x43/0x90
[  449.173987]        [<c0103214>] common_interrupt+0x24/0x40
[  449.174147]        [<c010321e>] common_interrupt+0x2e/0x40
[  449.174308]        [<ffffffff>] 0xffffffff
[  449.174767] 
[  449.174769] -> #0 (&tbl->lock){-+-+}:
[  449.174939]        [<c01324f0>] print_circular_bug_entry+0x40/0x50
[  449.175108]        [<c0134a71>] __lock_acquire+0x971/0xf90
[  449.175268]        [<c013425e>] __lock_acquire+0x15e/0xf90
[  449.175468]        [<c0133c16>] trace_hardirqs_on+0x66/0x110
[  449.175633]        [<c01350ef>] lock_acquire+0x5f/0x80
[  449.175793]        [<c023d5a3>] neigh_lookup+0x43/0xb0
[  449.175973]        [<c029b2fe>] _read_lock_bh+0x2e/0x40
[  449.176139]        [<c023d5a3>] neigh_lookup+0x43/0xb0
[  449.176303]        [<c023d5a3>] neigh_lookup+0x43/0xb0
[  449.177821]        [<c8a74a8c>] ndisc_dst_alloc+0x13c/0x1a0 [ipv6]
[  449.177821]        [<c8a74950>] ndisc_dst_alloc+0x0/0x1a0 [ipv6]
[  449.177821]        [<c8a78575>] __ndisc_send+0x95/0x4e0 [ipv6]
[  449.177821]        [<c8a67410>] ip6_output+0x0/0xb00 [ipv6]
[  449.177821]        [<c8a79467>] ndisc_send_ns+0x67/0xa0 [ipv6]
[  449.177821]        [<c8a6eeb0>] ipv6_chk_addr+0xa0/0xb0 [ipv6]
[  449.177821]        [<c8a7a4ef>] ndisc_solicit+0x9f/0x1b0 [ipv6]
[  449.177821]        [<c0133af8>] mark_held_locks+0x38/0x70
[  449.177821]        [<c029b665>] _spin_unlock_irqrestore+0x45/0x60
[  449.177821]        [<c0133c16>] trace_hardirqs_on+0x66/0x110
[  449.177821]        [<c023fab5>] neigh_timer_handler+0x155/0x2a0
[  449.177821]        [<c011dd5f>] run_timer_softirq+0x15f/0x1c0
[  449.177821]        [<c023f960>] neigh_timer_handler+0x0/0x2a0
[  449.177821]        [<c023f960>] neigh_timer_handler+0x0/0x2a0
[  449.177821]        [<c011a182>] __do_softirq+0x52/0xb0
[  449.177821]        [<c011a225>] do_softirq+0x45/0x50
[  449.177821]        [<c011a665>] irq_exit+0x55/0x70
[  449.177821]        [<c0104e83>] do_IRQ+0x43/0x90
[  449.177821]        [<c0103214>] common_interrupt+0x24/0x40
[  449.177821]        [<c010321e>] common_interrupt+0x2e/0x40
[  449.177821]        [<c0101ace>] default_idle+0x5e/0x90
[  449.177821]        [<c0101a70>] default_idle+0x0/0x90
[  449.177821]        [<c0101910>] cpu_idle+0x30/0x80
[  449.177821]        [<ffffffff>] 0xffffffff
[  449.177821] 
[  449.177821] other info that might help us debug this:
[  449.177821] 
[  449.177821] 1 lock held by swapper/0:
[  449.177821]  #0:  (&n->lock){-+-+}, at: [<c023f975>] 
neigh_timer_handler+0x15/0x2a0
[  449.177821] 
[  449.177821] stack backtrace:
[  449.177821] Pid: 0, comm: swapper Not tainted 2.6.25-rc2 #67
[  449.177821]  [<c0132d72>] print_circular_bug_tail+0x72/0x80
[  449.177821]  [<c0134a71>] __lock_acquire+0x971/0xf90
[  449.177821]  [<c013425e>] __lock_acquire+0x15e/0xf90
[  449.177821]  [<c0133c16>] trace_hardirqs_on+0x66/0x110
[  449.177821]  [<c01350ef>] lock_acquire+0x5f/0x80
[  449.177821]  [<c023d5a3>] neigh_lookup+0x43/0xb0
[  449.177821]  [<c029b2fe>] _read_lock_bh+0x2e/0x40
[  449.177821]  [<c023d5a3>] neigh_lookup+0x43/0xb0
[  449.177821]  [<c023d5a3>] neigh_lookup+0x43/0xb0
[  449.177821]  [<c8a74a8c>] ndisc_dst_alloc+0x13c/0x1a0 [ipv6]
[  449.177821]  [<c8a74950>] ndisc_dst_alloc+0x0/0x1a0 [ipv6]
[  449.177821]  [<c8a78575>] __ndisc_send+0x95/0x4e0 [ipv6]
[  449.177821]  [<c8a67410>] ip6_output+0x0/0xb00 [ipv6]
[  449.177821]  [<c8a79467>] ndisc_send_ns+0x67/0xa0 [ipv6]
[  449.177821]  [<c8a6eeb0>] ipv6_chk_addr+0xa0/0xb0 [ipv6]
[  449.177821]  [<c8a7a4ef>] ndisc_solicit+0x9f/0x1b0 [ipv6]
[  449.177821]  [<c0133af8>] mark_held_locks+0x38/0x70
[  449.177821]  [<c029b665>] _spin_unlock_irqrestore+0x45/0x60
[  449.177821]  [<c0133c16>] trace_hardirqs_on+0x66/0x110
[  449.177821]  [<c023fab5>] neigh_timer_handler+0x155/0x2a0
[  449.177821]  [<c011dd5f>] run_timer_softirq+0x15f/0x1c0
[  449.177821]  [<c023f960>] neigh_timer_handler+0x0/0x2a0
[  449.177821]  [<c023f960>] neigh_timer_handler+0x0/0x2a0
[  449.177821]  [<c011a182>] __do_softirq+0x52/0xb0
[  449.177821]  [<c011a225>] do_softirq+0x45/0x50
[  449.177821]  [<c011a665>] irq_exit+0x55/0x70
[  449.177821]  [<c0104e83>] do_IRQ+0x43/0x90
[  449.177821]  [<c0103214>] common_interrupt+0x24/0x40
[  449.177821]  [<c010321e>] common_interrupt+0x2e/0x40
[  449.177821]  [<c0101ace>] default_idle+0x5e/0x90
[  449.177821]  [<c0101a70>] default_idle+0x0/0x90
[  449.177821]  [<c0101910>] cpu_idle+0x30/0x80
[  449.177821]  =======================

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: lockdep warnings in ipv6
  2008-02-24 12:10 lockdep warnings in ipv6 Jan Engelhardt
@ 2008-02-24 13:12 ` Kristof Provost
  2008-02-25  1:16 ` David Miller
  1 sibling, 0 replies; 3+ messages in thread
From: Kristof Provost @ 2008-02-24 13:12 UTC (permalink / raw)
  To: Jan Engelhardt; +Cc: netdev, Linux Kernel Mailing List

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 2008-02-24 13:10:58 (+0100), Jan Engelhardt <jengelh@computergmbh.de> wrote:
> Hi,
> 
> 
> when doing IPv6 (ping6, ssh otherhost, etc.), lockdep spews a warning in 
> 2.6.25-rc2 on the target. CONFIG_..._FRAME_POINTER is off,
I think that's the same bug I ran into. It was introduced in
69cc64d8d9 and reversed in 9ff56607468. I think Linus' tree has the
reversal by now.

Kristof
 
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=CPho
-----END PGP SIGNATURE-----

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: lockdep warnings in ipv6
  2008-02-24 12:10 lockdep warnings in ipv6 Jan Engelhardt
  2008-02-24 13:12 ` Kristof Provost
@ 2008-02-25  1:16 ` David Miller
  1 sibling, 0 replies; 3+ messages in thread
From: David Miller @ 2008-02-25  1:16 UTC (permalink / raw)
  To: jengelh; +Cc: netdev, linux-kernel

From: Jan Engelhardt <jengelh@computergmbh.de>
Date: Sun, 24 Feb 2008 13:10:58 +0100 (CET)

> when doing IPv6 (ping6, ssh otherhost, etc.), lockdep spews a warning in 
> 2.6.25-rc2 on the target. CONFIG_..._FRAME_POINTER is off,

We reverted the change which causes this, and it results
in real bonafide lockups too :-)

commit 9ff566074689e3aed1488780b97714ec43ba361d
Author: David S. Miller <davem@davemloft.net>
Date:   Sun Feb 17 18:39:54 2008 -0800

    Revert "[NDISC]: Fix race in generic address resolution"
    
    This reverts commit 69cc64d8d92bf852f933e90c888dfff083bd4fc9.
    
    It causes recursive locking in IPV6 because unlike other
    neighbour layer clients, it even needs neighbour cache
    entries to send neighbour soliciation messages :-(
    
    We'll have to find another way to fix this race.
    
    Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 7bb6a9a..a16cf1e 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -834,12 +834,18 @@ static void neigh_timer_handler(unsigned long arg)
 	}
 	if (neigh->nud_state & (NUD_INCOMPLETE | NUD_PROBE)) {
 		struct sk_buff *skb = skb_peek(&neigh->arp_queue);
-
+		/* keep skb alive even if arp_queue overflows */
+		if (skb)
+			skb_get(skb);
+		write_unlock(&neigh->lock);
 		neigh->ops->solicit(neigh, skb);
 		atomic_inc(&neigh->probes);
-	}
+		if (skb)
+			kfree_skb(skb);
+	} else {
 out:
-	write_unlock(&neigh->lock);
+		write_unlock(&neigh->lock);
+	}
 
 	if (notify)
 		neigh_update_notify(neigh);
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index c663fa5..8e17f65 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -368,6 +368,7 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
 		if (!(neigh->nud_state&NUD_VALID))
 			printk(KERN_DEBUG "trying to ucast probe in NUD_INVALID\n");
 		dst_ha = neigh->ha;
+		read_lock_bh(&neigh->lock);
 	} else if ((probes -= neigh->parms->app_probes) < 0) {
 #ifdef CONFIG_ARPD
 		neigh_app_ns(neigh);
@@ -377,6 +378,8 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
 
 	arp_send(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
 		 dst_ha, dev->dev_addr, NULL);
+	if (dst_ha)
+		read_unlock_bh(&neigh->lock);
 }
 
 static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)

^ permalink raw reply	[flat|nested] 3+ messages in thread

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2008-02-24 13:12 ` Kristof Provost
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