Messages in this thread Patch in this message | | | Subject | Re: 2.6.38-rc1: arp triggers RTNL assertion | From | Eric Dumazet <> | Date | Fri, 21 Jan 2011 19:52:56 +0100 |
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Le vendredi 21 janvier 2011 à 08:12 +0100, Eric Dumazet a écrit : > Le jeudi 20 janvier 2011 à 22:17 -0800, Jamie Heilman a écrit : > > With 2.6.38-rc1 when I run: arp -Ds 192.168.2.41 eth0 pub > > I see: > > > > RTNL: assertion failed at net/core/neighbour.c (589) > > Pid: 2330, comm: arp Not tainted 2.6.38-rc1-00132-g8d99641-dirty #1 > > Call Trace: > > [<c11ed339>] ? pneigh_lookup+0xc3/0x168 > > [<c1219f27>] ? arp_req_set+0x86/0x1d5 > > [<c11e74b5>] ? dev_get_by_name_rcu+0x72/0x7f > > [<c121a1a3>] ? arp_ioctl+0x12d/0x22e > > [<c121dfeb>] ? inet_ioctl+0x82/0xa7 > > [<c11d8ffc>] ? sock_ioctl+0x1b7/0x1db > > [<c11d8e45>] ? sock_ioctl+0x0/0x1db > > [<c108f02f>] ? do_vfs_ioctl+0x47c/0x4c5 > > [<c101803c>] ? do_page_fault+0x315/0x341 > > [<c11daaf3>] ? sys_socket+0x44/0x5a > > [<c11dab71>] ? sys_socketcall+0x68/0x270 > > [<c108f0ab>] ? sys_ioctl+0x33/0x4b > > [<c1002897>] ? sysenter_do_call+0x12/0x26 > > > > Figured I'd Cc Eric as this could be related to commit 941666c2, > > "net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()" > > > > Config attached, just in case (the uncommited change, in the tree this > > kernel was built from, is just Chuck Lever's recent nfs3xdr.c patch). > > Thanks for the report, I am looking at this right now. > >
Here is how I fixed this, thanks again Jamie !
[PATCH] net: neighbour: pneigh_lookup() doesnt need RTNL
Commit 941666c2 "net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()" introduced a regression, reported by Jamie Heilman. "arp -Ds 192.168.2.41 eth0 pub" triggered the ASSERT_RTNL() assert.
Relax pneigh_lookup() to not require RTNL being held, using the tbl rwlock, in read or write mode for the whole function duration.
Reported-by: Jamie Heilman <jamie@audible.transient.net> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> --- net/core/neighbour.c | 17 ++++++++++------- 1 files changed, 10 insertions(+), 7 deletions(-)
diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 799f06e..6b96b2c 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -578,17 +578,18 @@ struct pneigh_entry * pneigh_lookup(struct neigh_table *tbl, int key_len = tbl->key_len; u32 hash_val = pneigh_hash(pkey, key_len); - read_lock_bh(&tbl->lock); + if (creat) + write_lock_bh(&tbl->lock); + else + read_lock_bh(&tbl->lock); + n = __pneigh_lookup_1(tbl->phash_buckets[hash_val], net, pkey, key_len, dev); - read_unlock_bh(&tbl->lock); if (n || !creat) goto out; - ASSERT_RTNL(); - - n = kmalloc(sizeof(*n) + key_len, GFP_KERNEL); + n = kmalloc(sizeof(*n) + key_len, GFP_ATOMIC); if (!n) goto out; @@ -607,11 +608,13 @@ struct pneigh_entry * pneigh_lookup(struct neigh_table *tbl, goto out; } - write_lock_bh(&tbl->lock); n->next = tbl->phash_buckets[hash_val]; tbl->phash_buckets[hash_val] = n; - write_unlock_bh(&tbl->lock); out: + if (creat) + write_unlock_bh(&tbl->lock); + else + read_unlock_bh(&tbl->lock); return n; } EXPORT_SYMBOL(pneigh_lookup);
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