From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [LOCKDEP BUG][2.6.36-rc1] xt_info_wrlock? Date: Mon, 16 Aug 2010 19:31:33 +0200 Message-ID: <1281979893.2524.54.camel@edumazet-laptop> References: <1281978469.3268.55.camel@gandalf.stny.rr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: netdev@vger.kernel.org, LKML , "David S. Miller" , Patrick McHardy To: Steven Rostedt Return-path: In-Reply-To: <1281978469.3268.55.camel@gandalf.stny.rr.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Le lundi 16 ao=C3=BBt 2010 =C3=A0 13:07 -0400, Steven Rostedt a =C3=A9c= rit : > Hi, I hit this when booting 2.6.36-rc1: >=20 > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > [ 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: [] ip6t_do_ta= ble+0x8a/0x3f1 [ip6_tables] > {SOFTIRQ-ON-W} state was registered at: > [] __lock_acquire+0x756/0x93c > [] lock_acquire+0x100/0x12d > [] _raw_spin_lock+0x40/0x73 > [] get_counters+0xb2/0x168 [ip6_tables] > [] alloc_counters+0x3c/0x47 [ip6_tables] > [] do_ip6t_get_ctl+0x10c/0x363 [ip6_tables] > [] nf_sockopt+0x5a/0x86 > [] nf_getsockopt+0x18/0x1a > [] ipv6_getsockopt+0x84/0xba [ipv6] > [] rawv6_getsockopt+0x42/0x4b [ipv6] > [] sock_common_getsockopt+0x14/0x16 > [] sys_getsockopt+0x7a/0x9b > [] system_call_fastpath+0x16/0x1b > irq event stamp: 40 > hardirqs last enabled at (40): [] _raw_spin_unlock= _irqrestore+0x47/0x79 > hardirqs last disabled at (39): [] _raw_spin_lock_i= rqsave+0x2b/0x92 > softirqs last enabled at (0): [] copy_process+0x40= e/0x11ce > softirqs last disabled at (9): [] call_softirq+0x1c= /0x30 >=20 > other info that might help us debug this: > 3 locks held by ifup-eth/3288: > #0: (&idev->mc_ifc_timer){+.-...}, at: [] run_tim= er_softirq+0x1f5/0x3e6 > #1: (rcu_read_lock){.+.+..}, at: [] mld_sendpack+= 0x0/0x3ab [ipv6] > #2: (rcu_read_lock){.+.+..}, at: [] nf_hook_slow+= 0x0/0x119 >=20 > stack backtrace: > Pid: 3288, comm: ifup-eth Not tainted 2.6.36-rc1 #2937 > Call Trace: > [] print_usage_bug+0x1a4/0x1b5 > [] ? save_stack_trace+0x2f/0x4c > [] ? local_clock+0x40/0x59 > [] ? check_usage_forwards+0x0/0xcf > [] mark_lock+0x2ea/0x51f > [] __lock_acquire+0x6dc/0x93c > [] ? local_clock+0x40/0x59 > [] ? ip6t_do_table+0x8a/0x3f1 [ip6_tables] > [] lock_acquire+0x100/0x12d > [] ? ip6t_do_table+0x8a/0x3f1 [ip6_tables] > [] ? sched_clock+0x9/0xd > [] _raw_spin_lock+0x40/0x73 > [] ? ip6t_do_table+0x8a/0x3f1 [ip6_tables] > [] ip6t_do_table+0x8a/0x3f1 [ip6_tables] > [] ? trace_hardirqs_off_caller+0x1f/0x9e > [] ? nf_hook_slow+0x0/0x119 > [] ip6table_filter_hook+0x1c/0x20 [ip6table_filter= ] > [] nf_iterate+0x46/0x89 > [] ? dst_output+0x0/0x5c [ipv6] > [] nf_hook_slow+0x98/0x119 > [] ? dst_output+0x0/0x5c [ipv6] > [] ? icmp6_dst_alloc+0x0/0x1b2 [ipv6] > [] mld_sendpack+0x237/0x3ab [ipv6] > [] ? local_bh_enable_ip+0xc7/0xeb > [] mld_ifc_timer_expire+0x254/0x28d [ipv6] > [] run_timer_softirq+0x2c6/0x3e6 > [] ? run_timer_softirq+0x1f5/0x3e6 > [] ? mld_ifc_timer_expire+0x0/0x28d [ipv6] > [] ? __do_softirq+0x79/0x247 > [] __do_softirq+0x13e/0x247 > [] call_softirq+0x1c/0x30 > [] do_softirq+0x4b/0xa3 > [] irq_exit+0x4a/0x95 > [] smp_apic_timer_interrupt+0x8c/0x9a > [] apic_timer_interrupt+0x13/0x20 > [] ? native_flush_tlb_global+0x2b/0x32 > [] kernel_map_pages+0x12c/0x142 > [] free_pages_prepare+0x14c/0x15d > [] free_hot_cold_page+0x2d/0x165 > [] __free_pages+0x2b/0x34 > [] free_pages+0x49/0x4e > [] pgd_free+0x71/0x79 > [] __mmdrop+0x27/0x54 > [] finish_task_switch+0xb4/0xe4 > [] ? finish_task_switch+0x0/0xe4 > [] ? __switch_to+0x1a9/0x297 > [] schedule_tail+0x30/0xa7 > [] ret_from_fork+0x13/0x80 >=20 > I noticed in net/ipv6/netfilter/ip6_tables.c in get_counters() as wit= h > other "get_counters()" functions do not block bottom halves anymore a= s > to this commit: >=20 > commit 24b36f0193467fa727b85b4c004016a8dae999b9 > Author: Eric Dumazet > Date: Mon Aug 2 16:49:01 2010 +0200 >=20 > netfilter: {ip,ip6,arp}_tables: dont block bottom half more than = necessary > =20 > We currently disable BH for the whole duration of get_counters() >=20 > Now we take xt_info_wrlock(cpu) lock out of BH disabling. And that lo= ck > even has the following comment: >=20 > /* > * 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) >=20 >=20 > As lockdep has proven, this is not satisfied. >=20 > -- Steve >=20 >=20 This is a false positive, and a patch was sent yesterday http://patchwork.ozlabs.org/patch/61750/ Thanks