On Thu, Apr 23, 2015 at 10:07 AM, Josh Boyer <jwbo...@fedoraproject.org> wrote:
> [ 29.382235] br0: port 1(tap0) entered forwarding state
>
> [ 29.382286] ===============================
> [ 29.382315] [ INFO: suspicious RCU usage. ]
> [ 29.382344] 4.1.0-0.rc0.git11.1.fc23.x86_64 #1 Not tainted
> [ 29.382380] -------------------------------
> [ 29.382409] net/bridge/br_private.h:626 suspicious
> rcu_dereference_check() usage!
> [ 29.382455]
> other info that might help us debug this:
>
> [ 29.382507]
> rcu_scheduler_active = 1, debug_locks = 0
> [ 29.382549] 2 locks held by swapper/0/0:
> [ 29.382576] #0: (((&p->forward_delay_timer))){+.-...}, at:
> [<ffffffff81139f75>] call_timer_fn+0x5/0x4f0
> [ 29.382660] #1: (&(&br->lock)->rlock){+.-...}, at:
> [<ffffffffa0450dc1>] br_forward_delay_timer_expired+0x31/0x140
> [bridge]
> [ 29.382754]
> stack backtrace:
> [ 29.382787] CPU: 0 PID: 0 Comm: swapper/0 Not tainted
> 4.1.0-0.rc0.git11.1.fc23.x86_64 #1
> [ 29.382838] Hardware name: LENOVO 422916G/LENOVO, BIOS A1KT53AUS 04/07/2015
> [ 29.382882] 0000000000000000 3ebfc20364115825 ffff880666603c48
> ffffffff81892d4b
> [ 29.382943] 0000000000000000 ffffffff81e124e0 ffff880666603c78
> ffffffff8110bcd7
> [ 29.383004] ffff8800785c9d00 ffff88065485ac58 ffff880c62002800
> ffff880c5fc88ac0
> [ 29.383065] Call Trace:
> [ 29.383084] <IRQ> [<ffffffff81892d4b>] dump_stack+0x4c/0x65
> [ 29.383130] [<ffffffff8110bcd7>] lockdep_rcu_suspicious+0xe7/0x120
> [ 29.383178] [<ffffffffa04520f9>] br_fill_ifinfo+0x4a9/0x6a0 [bridge]
> [ 29.383225] [<ffffffffa045266b>] br_ifinfo_notify+0x11b/0x4b0 [bridge]
> [ 29.383271] [<ffffffffa0450d90>] ? br_hold_timer_expired+0x70/0x70
> [bridge]
> [ 29.383320] [<ffffffffa0450de8>]
> br_forward_delay_timer_expired+0x58/0x140 [bridge]
> [ 29.383371] [<ffffffffa0450d90>] ? br_hold_timer_expired+0x70/0x70
> [bridge]
> [ 29.383416] [<ffffffff8113a033>] call_timer_fn+0xc3/0x4f0
> [ 29.383454] [<ffffffff81139f75>] ? call_timer_fn+0x5/0x4f0
> [ 29.383493] [<ffffffff8110a90f>] ? lock_release_holdtime.part.29+0xf/0x200
> [ 29.383541] [<ffffffffa0450d90>] ? br_hold_timer_expired+0x70/0x70
> [bridge]
> [ 29.383587] [<ffffffff8113a6a4>] run_timer_softirq+0x244/0x490
> [ 29.383629] [<ffffffff810b68cc>] __do_softirq+0xec/0x670
> [ 29.383666] [<ffffffff810b70d5>] irq_exit+0x145/0x150
> [ 29.383703] [<ffffffff8189f506>] smp_apic_timer_interrupt+0x46/0x60
> [ 29.383744] [<ffffffff8189d523>] apic_timer_interrupt+0x73/0x80
> [ 29.383782] <EOI> [<ffffffff816f131f>] ? cpuidle_enter_state+0x5f/0x2f0
> [ 29.383832] [<ffffffff816f131b>] ? cpuidle_enter_state+0x5b/0x2f0
> [ 29.383873] [<ffffffff816f15e7>] cpuidle_enter+0x17/0x20
> [ 29.383908] [<ffffffff81103c6f>] cpu_startup_entry+0x36f/0x5f0
> [ 29.383949] [<ffffffff81887cbd>] rest_init+0x13d/0x150
> [ 29.383986] [<ffffffff821c905b>] start_kernel+0x4d2/0x4f3
> [ 29.384023] [<ffffffff821c8120>] ? early_idt_handlers+0x120/0x120
> [ 29.384064] [<ffffffff821c8339>] x86_64_start_reservations+0x2a/0x2c
> [ 29.384105] [<ffffffff821c8485>] x86_64_start_kernel+0x14a/0x16d
We are dereferencing a RCU pointer with rtnl assert, but in the timer context
we only have br->lock. It looks like we need to take RCU read lock on that path
rather than asserting rtnl lock.
Thanks for the report.
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