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    SubjectRe: mmotm 2010-04-28 - RCU whinges
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    Le lundi 03 mai 2010 à 07:38 +0200, Eric Dumazet a écrit :
    > Le dimanche 02 mai 2010 à 13:46 -0400, Valdis.Kletnieks@vt.edu a écrit :
    > > On Wed, 28 Apr 2010 16:53:32 PDT, akpm@linux-foundation.org said:
    > > > The mm-of-the-moment snapshot 2010-04-28-16-53 has been uploaded to
    > > >
    > > > http://userweb.kernel.org/~akpm/mmotm/
    > >
    > > I thought we swatted all these, hit another one...
    > >
    > > [ 9.131490] ctnetlink v0.93: registering with nfnetlink.
    > > [ 9.131535]
    > > [ 9.131535] ===================================================
    > > [ 9.131704] [ INFO: suspicious rcu_dereference_check() usage. ]
    > > [ 9.131794] ---------------------------------------------------
    > > [ 9.131883] net/netfilter/nf_conntrack_ecache.c:88 invoked rcu_dereference_check() without protection!
    > > [ 9.131977]
    > > [ 9.131977] other info that might help us debug this:
    > > [ 9.131978]
    > > [ 9.132218]
    > > [ 9.132219] rcu_scheduler_active = 1, debug_locks = 0
    > > [ 9.132434] 1 lock held by swapper/1:
    > > [ 9.132519] #0: (nf_ct_ecache_mutex){+.+...}, at: [<ffffffff8148922d>] nf_conntrack_register_notifier+0x1a/0x75
    > > [ 9.132938]
    > > [ 9.132939] stack backtrace:
    > > [ 9.133129] Pid: 1, comm: swapper Tainted: G W 2.6.34-rc5-mmotm0428 #1
    > > [ 9.133220] Call Trace:
    > > [ 9.133319] [<ffffffff81064832>] lockdep_rcu_dereference+0xaa/0xb2
    > > [ 9.133410] [<ffffffff81489250>] nf_conntrack_register_notifier+0x3d/0x75
    > > [ 9.133521] [<ffffffff81b5a157>] ctnetlink_init+0x71/0xd5
    > > [ 9.133627] [<ffffffff81b5a0e6>] ? ctnetlink_init+0x0/0xd5
    > > [ 9.133735] [<ffffffff810001ef>] do_one_initcall+0x59/0x14e
    > > [ 9.133843] [<ffffffff81b2e68a>] kernel_init+0x144/0x1ce
    > > [ 9.133949] [<ffffffff81003414>] kernel_thread_helper+0x4/0x10
    > > [ 9.134060] [<ffffffff81598a40>] ? restore_args+0x0/0x30
    > > [ 9.134196] [<ffffffff81b2e546>] ? kernel_init+0x0/0x1ce
    > > [ 9.134328] [<ffffffff81003410>] ? kernel_thread_helper+0x0/0x10
    > > [ 9.134530] ip_tables: (C) 2000-2006 Netfilter Core Team
    > > [ 9.134655] TCP bic registered
    > >
    >
    > Thanks for the report !
    >
    > We can use rcu_dereference_protected() in those cases.
    >
    > [PATCH] net: Use rcu_dereference_protected in nf_conntrack_ecache
    >
    > Writers own nf_ct_ecache_mutex.
    >
    > Reported-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
    > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
    > ---


    Oops scratch that, I'll resend a correct version.



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