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SubjectRe: packet_sendmsg_spkt sleeping from invalid context
On Mon, Dec 14, 2009 at 08:24:23PM +0100, Eric Dumazet wrote:
> Le 14/12/2009 18:52, Frederic Weisbecker a écrit :
> > Hi,
> >
> > I don't know if it has been reported already.
> > I get the following warning on boot, with latest upstream tree:
> >
> > [ 32.776502] sched: BUG: sleeping function called from invalid context at mm/slab.c:3032
> > [ 32.802173] sched: in_atomic(): 1, irqs_disabled(): 0, pid: 3555, name: dhclient3
> > [ 32.821141] 1 lock held by dhclient3/3555:
> > [ 32.821147] #0: (rcu_read_lock){.+.+.+}, at: [<ffffffff815d177d>] packet_sendmsg_spkt+0x7d/0x2c0
> > [ 32.821174] Pid: 3555, comm: dhclient3 Tainted: G W 2.6.32-tip+ #134
> > [ 32.821181] Call Trace:
> > [ 32.821194] [<ffffffff810811c3>] ? __debug_show_held_locks+0x13/0x30
> > [ 32.821207] [<ffffffff8103d6b8>] __might_sleep+0x118/0x140
> > [ 32.821219] [<ffffffff81110c23>] kmem_cache_alloc+0x173/0x190
> > [ 32.821231] [<ffffffff815483d9>] __alloc_skb+0x49/0x170
> > [ 32.821241] [<ffffffff81542238>] sock_wmalloc+0x38/0x80
> > [ 32.821250] [<ffffffff815d182b>] packet_sendmsg_spkt+0x12b/0x2c0
> > [ 32.821260] [<ffffffff815d177d>] ? packet_sendmsg_spkt+0x7d/0x2c0
> > [ 32.821272] [<ffffffff8153ded7>] sock_sendmsg+0x127/0x140
> > [ 32.821285] [<ffffffff8106f4a0>] ? autoremove_wake_function+0x0/0x40
> > [ 32.821297] [<ffffffff810f467b>] ? might_fault+0x7b/0xd0
> > [ 32.821306] [<ffffffff810f467b>] ? might_fault+0x7b/0xd0
> > [ 32.821318] [<ffffffff815401aa>] ? move_addr_to_kernel+0x6a/0x70
> > [ 32.821328] [<ffffffff8154029f>] sys_sendto+0xef/0x120
> > [ 32.821340] [<ffffffff81131479>] ? mntput_no_expire+0x29/0x110
> > [ 32.821355] [<ffffffff810027db>] system_call_fastpath+0x16/0x1b
> >
>
> Thanks for the report Frederic.
>
> We could partly revert the original commit, but as we wanted to avoid touching
> device refcount, and af_packet might be the only real abuser, we could
> try following patch instead.
>
> Thanks



I also wonder. Are you using PREEMPT_RCU ?
That may explain why you haven't seen this issue because
might_sleep() doesn't see you are in a rcu read locked
section as preemption is not disabled, but it is illegal to
voluntarily sleep in such area (although it's fine with
preempt rcu) as doing so with non-prempt RCU config would barf.

I'm trying a patch to handle that.

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