This is a note to let you know that I've just added the patch titled
tipc: fix lockdep warning during bearer initialization
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tipc-fix-lockdep-warning-during-bearer-initialization.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f023235029429ba54960f51dc46ea98dfca16a9b Mon Sep 17 00:00:00 2001
From: Ying Xue <ying.xue@xxxxxxxxxxxxx>
Date: Thu, 16 Aug 2012 12:09:07 +0000
Subject: tipc: fix lockdep warning during bearer initialization
From: Ying Xue <ying.xue@xxxxxxxxxxxxx>
[ Upstream commit 4225a398c1352a7a5c14dc07277cb5cc4473983b ]
When the lockdep validator is enabled, it will report the below
warning when we enable a TIPC bearer:
[ INFO: possible irq lock inversion dependency detected ]
---------------------------------------------------------
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(ptype_lock);
local_irq_disable();
lock(tipc_net_lock);
lock(ptype_lock);
<Interrupt>
lock(tipc_net_lock);
*** DEADLOCK ***
the shortest dependencies between 2nd lock and 1st lock:
-> (ptype_lock){+.+...} ops: 10 {
[...]
SOFTIRQ-ON-W at:
[<c1089418>] __lock_acquire+0x528/0x13e0
[<c108a360>] lock_acquire+0x90/0x100
[<c1553c38>] _raw_spin_lock+0x38/0x50
[<c14651ca>] dev_add_pack+0x3a/0x60
[<c182da75>] arp_init+0x1a/0x48
[<c182dce5>] inet_init+0x181/0x27e
[<c1001114>] do_one_initcall+0x34/0x170
[<c17f7329>] kernel_init+0x110/0x1b2
[<c155b6a2>] kernel_thread_helper+0x6/0x10
[...]
... key at: [<c17e4b10>] ptype_lock+0x10/0x20
... acquired at:
[<c108a360>] lock_acquire+0x90/0x100
[<c1553c38>] _raw_spin_lock+0x38/0x50
[<c14651ca>] dev_add_pack+0x3a/0x60
[<c8bc18d2>] enable_bearer+0xf2/0x140 [tipc]
[<c8bb283a>] tipc_enable_bearer+0x1ba/0x450 [tipc]
[<c8bb3a04>] tipc_cfg_do_cmd+0x5c4/0x830 [tipc]
[<c8bbc032>] handle_cmd+0x42/0xd0 [tipc]
[<c148e802>] genl_rcv_msg+0x232/0x280
[<c148d3f6>] netlink_rcv_skb+0x86/0xb0
[<c148e5bc>] genl_rcv+0x1c/0x30
[<c148d144>] netlink_unicast+0x174/0x1f0
[<c148ddab>] netlink_sendmsg+0x1eb/0x2d0
[<c1456bc1>] sock_aio_write+0x161/0x170
[<c1135a7c>] do_sync_write+0xac/0xf0
[<c11360f6>] vfs_write+0x156/0x170
[<c11361e2>] sys_write+0x42/0x70
[<c155b0df>] sysenter_do_call+0x12/0x38
[...]
}
-> (tipc_net_lock){+..-..} ops: 4 {
[...]
IN-SOFTIRQ-R at:
[<c108953a>] __lock_acquire+0x64a/0x13e0
[<c108a360>] lock_acquire+0x90/0x100
[<c15541cd>] _raw_read_lock_bh+0x3d/0x50
[<c8bb874d>] tipc_recv_msg+0x1d/0x830 [tipc]
[<c8bc195f>] recv_msg+0x3f/0x50 [tipc]
[<c146a5fa>] __netif_receive_skb+0x22a/0x590
[<c146ab0b>] netif_receive_skb+0x2b/0xf0
[<c13c43d2>] pcnet32_poll+0x292/0x780
[<c146b00a>] net_rx_action+0xfa/0x1e0
[<c103a4be>] __do_softirq+0xae/0x1e0
[...]
}
>From the log, we can see three different call chains between
CPU0 and CPU1:
Time 0 on CPU0:
kernel_init()->inet_init()->dev_add_pack()
At time 0, the ptype_lock is held by CPU0 in dev_add_pack();
Time 1 on CPU1:
tipc_enable_bearer()->enable_bearer()->dev_add_pack()
At time 1, tipc_enable_bearer() first holds tipc_net_lock, and then
wants to take ptype_lock to register TIPC protocol handler into the
networking stack. But the ptype_lock has been taken by dev_add_pack()
on CPU0, so at this time the dev_add_pack() running on CPU1 has to be
busy looping.
Time 2 on CPU0:
netif_receive_skb()->recv_msg()->tipc_recv_msg()
At time 2, an incoming TIPC packet arrives at CPU0, hence
tipc_recv_msg() will be invoked. In tipc_recv_msg(), it first wants
to hold tipc_net_lock. At the moment, below scenario happens:
On CPU0, below is our sequence of taking locks:
lock(ptype_lock)->lock(tipc_net_lock)
On CPU1, our sequence of taking locks looks like:
lock(tipc_net_lock)->lock(ptype_lock)
Obviously deadlock may happen in this case.
But please note the deadlock possibly doesn't occur at all when the
first TIPC bearer is enabled. Before enable_bearer() -- running on
CPU1 does not hold ptype_lock, so the TIPC receive handler (i.e.
recv_msg()) is not registered successfully via dev_add_pack(), so
the tipc_recv_msg() cannot be called by recv_msg() even if a TIPC
message comes to CPU0. But when the second TIPC bearer is
registered, the deadlock can perhaps really happen.
To fix it, we will push the work of registering TIPC protocol
handler into workqueue context. After the change, both paths taking
ptype_lock are always in process contexts, thus, the deadlock should
never occur.
Signed-off-by: Ying Xue <ying.xue@xxxxxxxxxxxxx>
Signed-off-by: Jon Maloy <jon.maloy@xxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/tipc/eth_media.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
--- a/net/tipc/eth_media.c
+++ b/net/tipc/eth_media.c
@@ -53,6 +53,7 @@ struct eth_bearer {
struct tipc_bearer *bearer;
struct net_device *dev;
struct packet_type tipc_packet_type;
+ struct work_struct setup;
};
static struct eth_bearer eth_bearers[MAX_ETH_BEARERS];
@@ -121,6 +122,17 @@ static int recv_msg(struct sk_buff *buf,
}
/**
+ * setup_bearer - setup association between Ethernet bearer and interface
+ */
+static void setup_bearer(struct work_struct *work)
+{
+ struct eth_bearer *eb_ptr =
+ container_of(work, struct eth_bearer, setup);
+
+ dev_add_pack(&eb_ptr->tipc_packet_type);
+}
+
+/**
* enable_bearer - attach TIPC bearer to an Ethernet interface
*/
@@ -167,7 +179,8 @@ static int enable_bearer(struct tipc_bea
eb_ptr->tipc_packet_type.af_packet_priv = eb_ptr;
INIT_LIST_HEAD(&(eb_ptr->tipc_packet_type.list));
dev_hold(dev);
- dev_add_pack(&eb_ptr->tipc_packet_type);
+ INIT_WORK(&eb_ptr->setup, setup_bearer);
+ schedule_work(&eb_ptr->setup);
}
/* Associate TIPC bearer with Ethernet bearer */
Patches currently in stable-queue which might be from ying.xue@xxxxxxxxxxxxx are
queue-3.0/tipc-fix-lockdep-warning-during-bearer-initialization.patch
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