• Eric Dumazet's avatar
    bridge: fix lockdep splat · 93a33a58
    Eric Dumazet authored
    Following lockdep splat was reported :
    
    [   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
    
    Problem here is that br_forward_delay_timer_expired() is a timer
    handler, calling br_ifinfo_notify() which assumes either rcu_read_lock()
    or RTNL are held.
    
    Simplest fix seems to add rcu read lock section.
    Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
    Reported-by: default avatarJosh Boyer <jwboyer@fedoraproject.org>
    Reported-by: default avatarDominick Grift <dac.override@gmail.com>
    Cc: Vlad Yasevich <vyasevich@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    93a33a58
br_stp_timer.c 4.55 KB