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authorJon Maloy <donmalo99@gmail.com>2018-11-26 12:26:14 -0500
committerDavid S. Miller <davem@davemloft.net>2018-11-27 16:30:39 -0800
commitec835f891232d7763dea9da0358f31e24ca6dfb7 (patch)
tree3e7c7e6caee06163b89789bccf52f3a1f9d2e21a /net
parentcc5922054131f9abefdc0622ae64fc55e6b2671d (diff)
downloadlinux-stericsson-ec835f891232d7763dea9da0358f31e24ca6dfb7.tar.gz
tipc: fix lockdep warning during node delete
We see the following lockdep warning: [ 2284.078521] ====================================================== [ 2284.078604] WARNING: possible circular locking dependency detected [ 2284.078604] 4.19.0+ #42 Tainted: G E [ 2284.078604] ------------------------------------------------------ [ 2284.078604] rmmod/254 is trying to acquire lock: [ 2284.078604] 00000000acd94e28 ((&n->timer)#2){+.-.}, at: del_timer_sync+0x5/0xa0 [ 2284.078604] [ 2284.078604] but task is already holding lock: [ 2284.078604] 00000000f997afc0 (&(&tn->node_list_lock)->rlock){+.-.}, at: tipc_node_stop+0xac/0x190 [tipc] [ 2284.078604] [ 2284.078604] which lock already depends on the new lock. [ 2284.078604] [ 2284.078604] [ 2284.078604] the existing dependency chain (in reverse order) is: [ 2284.078604] [ 2284.078604] -> #1 (&(&tn->node_list_lock)->rlock){+.-.}: [ 2284.078604] tipc_node_timeout+0x20a/0x330 [tipc] [ 2284.078604] call_timer_fn+0xa1/0x280 [ 2284.078604] run_timer_softirq+0x1f2/0x4d0 [ 2284.078604] __do_softirq+0xfc/0x413 [ 2284.078604] irq_exit+0xb5/0xc0 [ 2284.078604] smp_apic_timer_interrupt+0xac/0x210 [ 2284.078604] apic_timer_interrupt+0xf/0x20 [ 2284.078604] default_idle+0x1c/0x140 [ 2284.078604] do_idle+0x1bc/0x280 [ 2284.078604] cpu_startup_entry+0x19/0x20 [ 2284.078604] start_secondary+0x187/0x1c0 [ 2284.078604] secondary_startup_64+0xa4/0xb0 [ 2284.078604] [ 2284.078604] -> #0 ((&n->timer)#2){+.-.}: [ 2284.078604] del_timer_sync+0x34/0xa0 [ 2284.078604] tipc_node_delete+0x1a/0x40 [tipc] [ 2284.078604] tipc_node_stop+0xcb/0x190 [tipc] [ 2284.078604] tipc_net_stop+0x154/0x170 [tipc] [ 2284.078604] tipc_exit_net+0x16/0x30 [tipc] [ 2284.078604] ops_exit_list.isra.8+0x36/0x70 [ 2284.078604] unregister_pernet_operations+0x87/0xd0 [ 2284.078604] unregister_pernet_subsys+0x1d/0x30 [ 2284.078604] tipc_exit+0x11/0x6f2 [tipc] [ 2284.078604] __x64_sys_delete_module+0x1df/0x240 [ 2284.078604] do_syscall_64+0x66/0x460 [ 2284.078604] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 2284.078604] [ 2284.078604] other info that might help us debug this: [ 2284.078604] [ 2284.078604] Possible unsafe locking scenario: [ 2284.078604] [ 2284.078604] CPU0 CPU1 [ 2284.078604] ---- ---- [ 2284.078604] lock(&(&tn->node_list_lock)->rlock); [ 2284.078604] lock((&n->timer)#2); [ 2284.078604] lock(&(&tn->node_list_lock)->rlock); [ 2284.078604] lock((&n->timer)#2); [ 2284.078604] [ 2284.078604] *** DEADLOCK *** [ 2284.078604] [ 2284.078604] 3 locks held by rmmod/254: [ 2284.078604] #0: 000000003368be9b (pernet_ops_rwsem){+.+.}, at: unregister_pernet_subsys+0x15/0x30 [ 2284.078604] #1: 0000000046ed9c86 (rtnl_mutex){+.+.}, at: tipc_net_stop+0x144/0x170 [tipc] [ 2284.078604] #2: 00000000f997afc0 (&(&tn->node_list_lock)->rlock){+.-.}, at: tipc_node_stop+0xac/0x19 [...} The reason is that the node timer handler sometimes needs to delete a node which has been disconnected for too long. To do this, it grabs the lock 'node_list_lock', which may at the same time be held by the generic node cleanup function, tipc_node_stop(), during module removal. Since the latter is calling del_timer_sync() inside the same lock, we have a potential deadlock. We fix this letting the timer cleanup function use spin_trylock() instead of just spin_lock(), and when it fails to grab the lock it just returns so that the timer handler can terminate its execution. This is safe to do, since tipc_node_stop() anyway is about to delete both the timer and the node instance. Fixes: 6a939f365bdb ("tipc: Auto removal of peer down node instance") Acked-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/tipc/node.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/net/tipc/node.c b/net/tipc/node.c
index 2afc4f8c37a7..488019766433 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -584,12 +584,15 @@ static void tipc_node_clear_links(struct tipc_node *node)
/* tipc_node_cleanup - delete nodes that does not
* have active links for NODE_CLEANUP_AFTER time
*/
-static int tipc_node_cleanup(struct tipc_node *peer)
+static bool tipc_node_cleanup(struct tipc_node *peer)
{
struct tipc_net *tn = tipc_net(peer->net);
bool deleted = false;
- spin_lock_bh(&tn->node_list_lock);
+ /* If lock held by tipc_node_stop() the node will be deleted anyway */
+ if (!spin_trylock_bh(&tn->node_list_lock))
+ return false;
+
tipc_node_write_lock(peer);
if (!node_is_up(peer) && time_after(jiffies, peer->delete_at)) {