diff options
| author | Pavel Emelyanov <xemul@parallels.com> | 2012-08-21 01:06:47 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-08-22 22:58:27 -0700 |
| commit | 0fa7fa98dbcc2789409ed24e885485e645803d7f (patch) | |
| tree | 30a9b851fdee3b01a64f5ee07940224d089d31de /net/packet/diag.c | |
| parent | b32607dd47d456b99f0a16f1c37bc8a0975ffb19 (diff) | |
| download | linux-0fa7fa98dbcc2789409ed24e885485e645803d7f.tar.bz2 | |
packet: Protect packet sk list with mutex (v2)
Change since v1:
* Fixed inuse counters access spotted by Eric
In patch eea68e2f (packet: Report socket mclist info via diag module) I've
introduced a "scheduling in atomic" problem in packet diag module -- the
socket list is traversed under rcu_read_lock() while performed under it sk
mclist access requires rtnl lock (i.e. -- mutex) to be taken.
[152363.820563] BUG: scheduling while atomic: crtools/12517/0x10000002
[152363.820573] 4 locks held by crtools/12517:
[152363.820581] #0: (sock_diag_mutex){+.+.+.}, at: [<ffffffff81a2dcb5>] sock_diag_rcv+0x1f/0x3e
[152363.820613] #1: (sock_diag_table_mutex){+.+.+.}, at: [<ffffffff81a2de70>] sock_diag_rcv_msg+0xdb/0x11a
[152363.820644] #2: (nlk->cb_mutex){+.+.+.}, at: [<ffffffff81a67d01>] netlink_dump+0x23/0x1ab
[152363.820693] #3: (rcu_read_lock){.+.+..}, at: [<ffffffff81b6a049>] packet_diag_dump+0x0/0x1af
Similar thing was then re-introduced by further packet diag patches (fanount
mutex and pgvec mutex for rings) :(
Apart from being terribly sorry for the above, I propose to change the packet
sk list protection from spinlock to mutex. This lock currently protects two
modifications:
* sklist
* prot inuse counters
The sklist modifications can be just reprotected with mutex since they already
occur in a sleeping context. The inuse counters modifications are trickier -- the
__this_cpu_-s are used inside, thus requiring the caller to handle the potential
issues with contexts himself. Since packet sockets' counters are modified in two
places only (packet_create and packet_release) we only need to protect the context
from being preempted. BH disabling is not required in this case.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/packet/diag.c')
| -rw-r--r-- | net/packet/diag.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/net/packet/diag.c b/net/packet/diag.c index bc33fbe8a5ef..39bce0d50df9 100644 --- a/net/packet/diag.c +++ b/net/packet/diag.c @@ -177,8 +177,8 @@ static int packet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb) net = sock_net(skb->sk); req = nlmsg_data(cb->nlh); - rcu_read_lock(); - sk_for_each_rcu(sk, node, &net->packet.sklist) { + mutex_lock(&net->packet.sklist_lock); + sk_for_each(sk, node, &net->packet.sklist) { if (!net_eq(sock_net(sk), net)) continue; if (num < s_num) @@ -192,7 +192,7 @@ next: num++; } done: - rcu_read_unlock(); + mutex_unlock(&net->packet.sklist_lock); cb->args[0] = num; return skb->len; |