On Thu, 2015-08-20 at 08:51 -0700, David Ahern wrote:
> Hit the following splat testing VRF change for ipsec:
>
> [ 113.475692] ===============================
> [ 113.476194] [ INFO: suspicious RCU usage. ]
> [ 113.476667] 4.2.0-rc6-1+deb7u2+clUNRELEASED #3.2.65-1+deb7u2+clUNRELEASED
> Not tainted
> [ 113.477545] -------------------------------
> [ 113.478013] /work/monster-14/dsa/kernel.git/include/linux/rcupdate.h:568
> Illegal context switch in RCU read-side critical section!
> [ 113.479288]
> [ 113.479288] other info that might help us debug this:
> [ 113.479288]
> [ 113.480207]
> [ 113.480207] rcu_scheduler_active = 1, debug_locks = 1
> [ 113.480931] 2 locks held by setkey/6829:
> [ 113.481371] #0: (&net->xfrm.xfrm_cfg_mutex){+.+.+.}, at:
> [<ffffffff814e9887>] pfkey_sendmsg+0xfb/0x213
> [ 113.482509] #1: (rcu_read_lock){......}, at: [<ffffffff814e767f>]
> rcu_read_lock+0x0/0x6e
> [ 113.483509]
> [ 113.483509] stack backtrace:
> [ 113.484041] CPU: 0 PID: 6829 Comm: setkey Not tainted
> 4.2.0-rc6-1+deb7u2+clUNRELEASED #3.2.65-1+deb7u2+clUNRELEASED
> [ 113.485422] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> rel-1.7.5.1-0-g8936dbb-20141113_115728-nilsson.home.kraxel.org 04/01/2014
> [ 113.486845] 0000000000000001 ffff88001d4c7a98 ffffffff81518af2
> ffffffff81086962
> [ 113.487732] ffff88001d538480 ffff88001d4c7ac8 ffffffff8107ae75
> ffffffff8180a154
> [ 113.488628] 0000000000000b30 0000000000000000 00000000000000d0
> ffff88001d4c7ad8
> [ 113.489525] Call Trace:
> [ 113.489813] [<ffffffff81518af2>] dump_stack+0x4c/0x65
> [ 113.490389] [<ffffffff81086962>] ? console_unlock+0x3d6/0x405
> [ 113.491039] [<ffffffff8107ae75>] lockdep_rcu_suspicious+0xfa/0x103
> [ 113.491735] [<ffffffff81064032>] rcu_preempt_sleep_check+0x45/0x47
> [ 113.492442] [<ffffffff8106404d>] ___might_sleep+0x19/0x1c8
> [ 113.493077] [<ffffffff81064268>] __might_sleep+0x6c/0x82
> [ 113.493681] [<ffffffff81133190>]
> cache_alloc_debugcheck_before.isra.50+0x1d/0x24
> [ 113.494508] [<ffffffff81134876>] kmem_cache_alloc+0x31/0x18f
> [ 113.495149] [<ffffffff814012b5>] skb_clone+0x64/0x80
> [ 113.495712] [<ffffffff814e6f71>] pfkey_broadcast_one+0x3d/0xff
> [ 113.496380] [<ffffffff814e7b84>] pfkey_broadcast+0xb5/0x11e
> [ 113.497024] [<ffffffff814e82d1>] pfkey_register+0x191/0x1b1
> [ 113.497653] [<ffffffff814e9770>] pfkey_process+0x162/0x17e
> [ 113.498274] [<ffffffff814e9895>] pfkey_sendmsg+0x109/0x213
>
> In pfkey_sendmsg the net mutex is taken and then pfkey_broadcast takes
> the RCU lock. Fix by using GFP_ATOMIC for the allocation flag.
>
> Signed-off-by: David Ahern <d...@cumulusnetworks.com>
> ---
> net/key/af_key.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/key/af_key.c b/net/key/af_key.c
> index b397f0aa9005..73527e7dd247 100644
> --- a/net/key/af_key.c
> +++ b/net/key/af_key.c
> @@ -1670,7 +1670,7 @@ static int pfkey_register(struct sock *sk, struct
> sk_buff *skb, const struct sad
> return -ENOBUFS;
> }
>
> - pfkey_broadcast(supp_skb, GFP_KERNEL, BROADCAST_REGISTERED, sk,
> sock_net(sk));
> + pfkey_broadcast(supp_skb, GFP_ATOMIC, BROADCAST_REGISTERED, sk,
> sock_net(sk));
>
> return 0;
> }
I would rather remove the useless rcu locking from pfkey_broadcast() if
a mutex properly protects the thing.
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