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Date: Mon, 16 Aug 2010 19:31:33 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: netdev@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
"David S. Miller" <davem@...emloft.net>,
Patrick McHardy <kaber@...sh.net>
Subject: Re: [LOCKDEP BUG][2.6.36-rc1] xt_info_wrlock?
Le lundi 16 août 2010 à 13:07 -0400, Steven Rostedt a écrit :
> Hi, I hit this when booting 2.6.36-rc1:
>
> =================================
> [ INFO: inconsistent lock state ]
> 2.6.36-rc1 #2937
> ---------------------------------
> inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
> ifup-eth/3288 [HC0[0]:SC1[2]:HE1:SE0] takes:
> (&(&lock->lock)->rlock){+.?...}, at: [<ffffffffa0166eef>] ip6t_do_table+0x8a/0x3f1 [ip6_tables]
> {SOFTIRQ-ON-W} state was registered at:
> [<ffffffff8107b08e>] __lock_acquire+0x756/0x93c
> [<ffffffff8107b374>] lock_acquire+0x100/0x12d
> [<ffffffff813f4ec3>] _raw_spin_lock+0x40/0x73
> [<ffffffffa01664b1>] get_counters+0xb2/0x168 [ip6_tables]
> [<ffffffffa01665a3>] alloc_counters+0x3c/0x47 [ip6_tables]
> [<ffffffffa0167a7b>] do_ip6t_get_ctl+0x10c/0x363 [ip6_tables]
> [<ffffffff813863a2>] nf_sockopt+0x5a/0x86
> [<ffffffff813863e6>] nf_getsockopt+0x18/0x1a
> [<ffffffffa034c1ff>] ipv6_getsockopt+0x84/0xba [ipv6]
> [<ffffffffa0353289>] rawv6_getsockopt+0x42/0x4b [ipv6]
> [<ffffffff81355571>] sock_common_getsockopt+0x14/0x16
> [<ffffffff813525bb>] sys_getsockopt+0x7a/0x9b
> [<ffffffff8100ad32>] system_call_fastpath+0x16/0x1b
> irq event stamp: 40
> hardirqs last enabled at (40): [<ffffffff813f5ad5>] _raw_spin_unlock_irqrestore+0x47/0x79
> hardirqs last disabled at (39): [<ffffffff813f5036>] _raw_spin_lock_irqsave+0x2b/0x92
> softirqs last enabled at (0): [<ffffffff8104975a>] copy_process+0x40e/0x11ce
> softirqs last disabled at (9): [<ffffffff8100bc9c>] call_softirq+0x1c/0x30
>
> other info that might help us debug this:
> 3 locks held by ifup-eth/3288:
> #0: (&idev->mc_ifc_timer){+.-...}, at: [<ffffffff8105841c>] run_timer_softirq+0x1f5/0x3e6
> #1: (rcu_read_lock){.+.+..}, at: [<ffffffffa03578ca>] mld_sendpack+0x0/0x3ab [ipv6]
> #2: (rcu_read_lock){.+.+..}, at: [<ffffffff81384f83>] nf_hook_slow+0x0/0x119
>
> stack backtrace:
> Pid: 3288, comm: ifup-eth Not tainted 2.6.36-rc1 #2937
> Call Trace:
> <IRQ> [<ffffffff81077ae6>] print_usage_bug+0x1a4/0x1b5
> [<ffffffff810164fa>] ? save_stack_trace+0x2f/0x4c
> [<ffffffff8106cd0c>] ? local_clock+0x40/0x59
> [<ffffffff810786b6>] ? check_usage_forwards+0x0/0xcf
> [<ffffffff81077de1>] mark_lock+0x2ea/0x51f
> [<ffffffff8107b014>] __lock_acquire+0x6dc/0x93c
> [<ffffffff8106cd0c>] ? local_clock+0x40/0x59
> [<ffffffffa0166eef>] ? ip6t_do_table+0x8a/0x3f1 [ip6_tables]
> [<ffffffff8107b374>] lock_acquire+0x100/0x12d
> [<ffffffffa0166eef>] ? ip6t_do_table+0x8a/0x3f1 [ip6_tables]
> [<ffffffff81011149>] ? sched_clock+0x9/0xd
> [<ffffffff813f4ec3>] _raw_spin_lock+0x40/0x73
> [<ffffffffa0166eef>] ? ip6t_do_table+0x8a/0x3f1 [ip6_tables]
> [<ffffffffa0166eef>] ip6t_do_table+0x8a/0x3f1 [ip6_tables]
> [<ffffffff810771db>] ? trace_hardirqs_off_caller+0x1f/0x9e
> [<ffffffff81384f83>] ? nf_hook_slow+0x0/0x119
> [<ffffffffa010601c>] ip6table_filter_hook+0x1c/0x20 [ip6table_filter]
> [<ffffffff81384f40>] nf_iterate+0x46/0x89
> [<ffffffffa035627b>] ? dst_output+0x0/0x5c [ipv6]
> [<ffffffff8138501b>] nf_hook_slow+0x98/0x119
> [<ffffffffa035627b>] ? dst_output+0x0/0x5c [ipv6]
> [<ffffffffa0349557>] ? icmp6_dst_alloc+0x0/0x1b2 [ipv6]
> [<ffffffffa0357b01>] mld_sendpack+0x237/0x3ab [ipv6]
> [<ffffffff81051475>] ? local_bh_enable_ip+0xc7/0xeb
> [<ffffffffa0358390>] mld_ifc_timer_expire+0x254/0x28d [ipv6]
> [<ffffffff810584ed>] run_timer_softirq+0x2c6/0x3e6
> [<ffffffff8105841c>] ? run_timer_softirq+0x1f5/0x3e6
> [<ffffffffa035813c>] ? mld_ifc_timer_expire+0x0/0x28d [ipv6]
> [<ffffffff8105169e>] ? __do_softirq+0x79/0x247
> [<ffffffff81051763>] __do_softirq+0x13e/0x247
> [<ffffffff8100bc9c>] call_softirq+0x1c/0x30
> [<ffffffff8100d32f>] do_softirq+0x4b/0xa3
> [<ffffffff8105120a>] irq_exit+0x4a/0x95
> [<ffffffff813fc185>] smp_apic_timer_interrupt+0x8c/0x9a
> [<ffffffff8100b753>] apic_timer_interrupt+0x13/0x20
> <EOI> [<ffffffff8102c72a>] ? native_flush_tlb_global+0x2b/0x32
> [<ffffffff81031fec>] kernel_map_pages+0x12c/0x142
> [<ffffffff810cc89a>] free_pages_prepare+0x14c/0x15d
> [<ffffffff810cc9c8>] free_hot_cold_page+0x2d/0x165
> [<ffffffff810ccb2b>] __free_pages+0x2b/0x34
> [<ffffffff810ccb7d>] free_pages+0x49/0x4e
> [<ffffffff81033871>] pgd_free+0x71/0x79
> [<ffffffff81048b1b>] __mmdrop+0x27/0x54
> [<ffffffff81042c62>] finish_task_switch+0xb4/0xe4
> [<ffffffff81042bae>] ? finish_task_switch+0x0/0xe4
> [<ffffffff810096e7>] ? __switch_to+0x1a9/0x297
> [<ffffffff81042df3>] schedule_tail+0x30/0xa7
> [<ffffffff8100ac33>] ret_from_fork+0x13/0x80
>
> I noticed in net/ipv6/netfilter/ip6_tables.c in get_counters() as with
> other "get_counters()" functions do not block bottom halves anymore as
> to this commit:
>
> commit 24b36f0193467fa727b85b4c004016a8dae999b9
> Author: Eric Dumazet <eric.dumazet@...il.com>
> Date: Mon Aug 2 16:49:01 2010 +0200
>
> netfilter: {ip,ip6,arp}_tables: dont block bottom half more than necessary
>
> We currently disable BH for the whole duration of get_counters()
>
> Now we take xt_info_wrlock(cpu) lock out of BH disabling. And that lock
> even has the following comment:
>
> /*
> * The "writer" side needs to get exclusive access to the lock,
> * regardless of readers. This must be called with bottom half
> * processing (and thus also preemption) disabled.
> */
> static inline void xt_info_wrlock(unsigned int cpu)
>
>
> As lockdep has proven, this is not satisfied.
>
> -- Steve
>
>
This is a false positive, and a patch was sent yesterday
http://patchwork.ozlabs.org/patch/61750/
Thanks
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