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Message-ID: <1322589661.2596.2.camel@edumazet-laptop>
Date: Tue, 29 Nov 2011 19:01:01 +0100
From: Eric Dumazet <eric.dumazet@...il.com>
To: Marc Aurele La France <tsi@...berta.ca>
Cc: netdev@...r.kernel.org
Subject: Re: RCU'ed dst_get_neighbour()
Le mardi 29 novembre 2011 à 10:44 -0700, Marc Aurele La France a écrit :
> Hi.
>
> Commit (1) seems to imply that all dst_get_neighbour() references now need
> to be wrapped with rcu_read_lock()/rcu_read_unlock() sequences. See (2)
> for one such proposed change.
>
> In the case I have here (ipoib), this commit results in ...
>
> ===================================================
> [ INFO: suspicious rcu_dereference_check() usage. ]
> ---------------------------------------------------
> include/net/dst.h:91 invoked rcu_dereference_check() without protection!
>
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 1, debug_locks = 1
> 4 locks held by kworker/3:1/630:
> #0: (ib_cm){.+.+.+}, at: [<ffffffff81055735>]
> process_one_work+0x1ab/0x4f9
> #1: ((&(&work->work)->work)){+.+.+.}, at: [<ffffffff81055735>]
> process_one_work+0x1ab/0x4f9
> #2: (rcu_read_lock_bh){.+....}, at: [<ffffffff81388216>]
> dev_queue_xmit+0x0/0x5ae
> #3: (_xmit_INFINIBAND){+.-...}, at: [<ffffffff8139eecc>]
> sch_direct_xmit+0x4d/0x22b
>
> stack backtrace:
> Pid: 630, comm: kworker/3:1 Not tainted 3.1.3-smp #1
> Call Trace:
> [<ffffffff8106c385>] lockdep_rcu_dereference+0x9b/0xa4
> [<ffffffff81351cda>] ipoib_start_xmit+0xf4/0x36f
> [<ffffffff81384215>] dev_hard_start_xmit+0x2a7/0x54f
> [<ffffffff8139eeef>] sch_direct_xmit+0x70/0x22b
> [<ffffffff8138851f>] dev_queue_xmit+0x309/0x5ae
> [<ffffffff81388216>] ? napi_gro_receive+0xb3/0xb3
> [<ffffffff813582d3>] ipoib_cm_rep_handler+0x208/0x248
> [<ffffffff81433e16>] ? _raw_spin_unlock_irqrestore+0x3d/0x5b
> [<ffffffff8135a912>] ipoib_cm_tx_handler+0x95/0x27f
> [<ffffffff8106d183>] ? __trace_hardirqs_on_caller+0x41/0x65
> [<ffffffff81327b29>] cm_process_work+0x26/0xbc
> [<ffffffff81328d74>] cm_rep_handler+0x274/0x2ae
> [<ffffffff81329582>] cm_work_handler+0x41/0x91
> [<ffffffff8105582c>] process_one_work+0x2a2/0x4f9
> [<ffffffff81055735>] ? process_one_work+0x1ab/0x4f9
> [<ffffffff810580c6>] ? worker_thread+0x4a/0x1ca
> [<ffffffff81329541>] ? cm_req_handler+0x355/0x355
> [<ffffffff81058175>] worker_thread+0xf9/0x1ca
> [<ffffffff8105807c>] ? gcwq_mayday_timeout+0x77/0x77
> [<ffffffff8105bfa3>] kthread+0x86/0x8e
> [<ffffffff81436b34>] kernel_thread_helper+0x4/0x10
> [<ffffffff8143425d>] ? retint_restore_args+0xe/0xe
> [<ffffffff8105bf1d>] ? kthread_stop+0x1cd/0x1cd
> [<ffffffff81436b30>] ? gs_change+0xb/0xb
>
> ===================================================
> [ INFO: suspicious rcu_dereference_check() usage. ]
> ---------------------------------------------------
> include/net/dst.h:91 invoked rcu_dereference_check() without protection!
>
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 1, debug_locks = 1
> 2 locks held by kworker/u:2/748:
> #0: ((name)){.+.+.+}, at: [<ffffffff81055735>]
> process_one_work+0x1ab/0x4f9
> #1: ((&port_priv->work)){+.+.+.}, at: [<ffffffff81055735>]
> process_one_work+0x1ab/0x4f9
>
> stack backtrace:
> Pid: 748, comm: kworker/u:2 Not tainted 3.1.3-smp #1
> Call Trace:
> [<ffffffff8106c385>] lockdep_rcu_dereference+0x9b/0xa4
> [<ffffffff81354e68>] ipoib_mcast_join_finish+0x362/0x48a
> [<ffffffff81355481>] ipoib_mcast_sendonly_join_complete+0x3b/0x174
> [<ffffffff813246b3>] mcast_work_handler+0xba/0x182
> [<ffffffff813248aa>] join_handler+0xe6/0xee
> [<ffffffff81322af1>] ib_sa_mcmember_rec_callback+0x51/0x5c
> [<ffffffff8132289c>] recv_handler+0x44/0x50
> [<ffffffff8131efca>] ib_mad_complete_recv+0xc3/0x125
> [<ffffffff8131debe>] ? find_mad_agent+0x13a/0x149
> [<ffffffff8131f30a>] ib_mad_recv_done_handler+0x2de/0x326
> [<ffffffff8131f3b0>] ib_mad_completion_handler+0x5e/0x91
> [<ffffffff8105582c>] process_one_work+0x2a2/0x4f9
> [<ffffffff81055735>] ? process_one_work+0x1ab/0x4f9
> [<ffffffff810580c6>] ? worker_thread+0x4a/0x1ca
> [<ffffffff8131f352>] ? ib_mad_recv_done_handler+0x326/0x326
> [<ffffffff81058175>] worker_thread+0xf9/0x1ca
> [<ffffffff8105807c>] ? gcwq_mayday_timeout+0x77/0x77
> [<ffffffff8105bfa3>] kthread+0x86/0x8e
> [<ffffffff81436b34>] kernel_thread_helper+0x4/0x10
> [<ffffffff8143425d>] ? retint_restore_args+0xe/0xe
> [<ffffffff8105bf1d>] ? kthread_stop+0x1cd/0x1cd
> [<ffffffff81436b30>] ? gs_change+0xb/0xb
>
> Comments/flames?
>
> Thanks.
>
> Marc.
>
> PS: Please reply-to-all as I am not subscribed to netdev.
>
> (1) http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=f2c31e32b378a6653f8de606149d963baf11d7d3
> (2) http://www.spinics.net/lists/netdev/msg179639.html
>
> +----------------------------------+----------------------------------+
> | Marc Aurele La France | work: 1-780-492-9310 |
> | Academic Information and | fax: 1-780-492-1729 |
> | Communications Technologies | email: tsi@...berta.ca |
> | 352 General Services Building +----------------------------------+
> | University of Alberta | |
> | Edmonton, Alberta | Standard disclaimers apply |
> | T6G 2H1 | |
> | CANADA | |
> +----------------------------------+----------------------------------+
Thanks for the report Marc, I'll take a look asap.
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