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    SubjectRe: mmotm 2010-04-28 - RCU whinges
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    Le lundi 03 mai 2010 à 10:30 -0400, Valdis.Kletnieks@vt.edu a écrit :

    >
    > I *really* thought we swatted a bunch of these - did the fixes not make it
    > into linux-next or -mm? Your patch fixed that one, but then:
    >
    > [ 9.128899] Netfilter messages via NETLINK v0.30.
    > [ 9.128919] nf_conntrack version 0.5.0 (16384 buckets, 65536 max)
    > [ 9.129108] CONFIG_NF_CT_ACCT is deprecated and will be removed soon. Please use
    > [ 9.129110] nf_conntrack.acct=1 kernel parameter, acct=1 nf_conntrack module option or
    > [ 9.129113] sysctl net.netfilter.nf_conntrack_acct=1 to enable it.
    > [ 9.129135] ctnetlink v0.93: registering with nfnetlink.
    > [ 9.129452] ip_tables: (C) 2000-2006 Netfilter Core Team
    > [ 9.129506]
    > [ 9.129507] ===================================================
    > [ 9.129683] [ INFO: suspicious rcu_dereference_check() usage. ]
    > [ 9.129777] ---------------------------------------------------
    > [ 9.129872] net/netfilter/nf_log.c:55 invoked rcu_dereference_check() without protection!
    > [ 9.129969]
    > [ 9.129969] other info that might help us debug this:
    > [ 9.129970]
    > [ 9.130232]
    > [ 9.130232] rcu_scheduler_active = 1, debug_locks = 0
    > [ 9.130407] 1 lock held by swapper/1:
    > [ 9.130525] #0: (nf_log_mutex){+.+...}, at: [<ffffffff81481154>] nf_log_register+0x57/0x10f
    > [ 9.130955]
    > [ 9.130956] stack backtrace:
    > [ 9.131162] Pid: 1, comm: swapper Tainted: G W 2.6.34-rc5-mmotm0428 #2
    > [ 9.131259] Call Trace:
    > [ 9.131370] [<ffffffff81064832>] lockdep_rcu_dereference+0xaa/0xb2
    > [ 9.131466] [<ffffffff814811db>] nf_log_register+0xde/0x10f
    > [ 9.131579] [<ffffffff81b5ca28>] ? log_tg_init+0x0/0x29
    > [ 9.131689] [<ffffffff81b5ca4d>] log_tg_init+0x25/0x29
    > [ 9.131800] [<ffffffff810001ef>] do_one_initcall+0x59/0x14e
    > [ 9.131912] [<ffffffff81b2e68a>] kernel_init+0x144/0x1ce
    > [ 9.132033] [<ffffffff81003414>] kernel_thread_helper+0x4/0x10
    > [ 9.132146] [<ffffffff81598a40>] ? restore_args+0x0/0x30
    > [ 9.132257] [<ffffffff81b2e546>] ? kernel_init+0x0/0x1ce
    > [ 9.132370] [<ffffffff81003410>] ? kernel_thread_helper+0x0/0x10
    > [ 9.132513] TCP bic registered
    >

    You probably know this PROVE_RCU thing is new and reserved to
    developpers ?

    We yet have to change all spots were a rcu_dereference() was used
    without rcu_read_lock(). Not a bug by itself, just lockdep is to be
    instructed not to shout.

    Maybe 30 patches already in, and maybe 30 other are still needed.



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