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authorNeil Horman <nhorman@tuxdriver.com>2010-03-16 08:14:33 +0000
committerDavid S. Miller <davem@davemloft.net>2010-03-16 14:15:45 -0700
commita2f46ee1ba5ee249ce2ca1ee7a7a0ac46529fb4f (patch)
treea791769005885ab26a3353b70940c635b63b3e8d /net/tipc
parentc3259c8a7060d480e8eb2166da0a99d6879146b4 (diff)
downloadlinux-2.6.34-ux500-a2f46ee1ba5ee249ce2ca1ee7a7a0ac46529fb4f.tar.gz
tipc: fix lockdep warning on address assignment
So in the forward porting of various tipc packages, I was constantly getting this lockdep warning everytime I used tipc-config to set a network address for the protocol: [ INFO: possible circular locking dependency detected ] 2.6.33 #1 tipc-config/1326 is trying to acquire lock: (ref_table_lock){+.-...}, at: [<ffffffffa0315148>] tipc_ref_discard+0x53/0xd4 [tipc] but task is already holding lock: (&(&entry->lock)->rlock#2){+.-...}, at: [<ffffffffa03150d5>] tipc_ref_lock+0x43/0x63 [tipc] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&(&entry->lock)->rlock#2){+.-...}: [<ffffffff8107b508>] __lock_acquire+0xb67/0xd0f [<ffffffff8107b78c>] lock_acquire+0xdc/0x102 [<ffffffff8145471e>] _raw_spin_lock_bh+0x3b/0x6e [<ffffffffa03152b1>] tipc_ref_acquire+0xe8/0x11b [tipc] [<ffffffffa031433f>] tipc_createport_raw+0x78/0x1b9 [tipc] [<ffffffffa031450b>] tipc_createport+0x8b/0x125 [tipc] [<ffffffffa030f221>] tipc_subscr_start+0xce/0x126 [tipc] [<ffffffffa0308fb2>] process_signal_queue+0x47/0x7d [tipc] [<ffffffff81053e0c>] tasklet_action+0x8c/0xf4 [<ffffffff81054bd8>] __do_softirq+0xf8/0x1cd [<ffffffff8100aadc>] call_softirq+0x1c/0x30 [<ffffffff810549f4>] _local_bh_enable_ip+0xb8/0xd7 [<ffffffff81054a21>] local_bh_enable_ip+0xe/0x10 [<ffffffff81454d31>] _raw_spin_unlock_bh+0x34/0x39 [<ffffffffa0308eb8>] spin_unlock_bh.clone.0+0x15/0x17 [tipc] [<ffffffffa0308f47>] tipc_k_signal+0x8d/0xb1 [tipc] [<ffffffffa0308dd9>] tipc_core_start+0x8a/0xad [tipc] [<ffffffffa01b1087>] 0xffffffffa01b1087 [<ffffffff8100207d>] do_one_initcall+0x72/0x18a [<ffffffff810872fb>] sys_init_module+0xd8/0x23a [<ffffffff81009b42>] system_call_fastpath+0x16/0x1b -> #0 (ref_table_lock){+.-...}: [<ffffffff8107b3b2>] __lock_acquire+0xa11/0xd0f [<ffffffff8107b78c>] lock_acquire+0xdc/0x102 [<ffffffff81454836>] _raw_write_lock_bh+0x3b/0x6e [<ffffffffa0315148>] tipc_ref_discard+0x53/0xd4 [tipc] [<ffffffffa03141ee>] tipc_deleteport+0x40/0x119 [tipc] [<ffffffffa0316e35>] release+0xeb/0x137 [tipc] [<ffffffff8139dbf4>] sock_release+0x1f/0x6f [<ffffffff8139dc6b>] sock_close+0x27/0x2b [<ffffffff811116f6>] __fput+0x12a/0x1df [<ffffffff811117c5>] fput+0x1a/0x1c [<ffffffff8110e49b>] filp_close+0x68/0x72 [<ffffffff8110e552>] sys_close+0xad/0xe7 [<ffffffff81009b42>] system_call_fastpath+0x16/0x1b Finally decided I should fix this. Its a straightforward inversion, tipc_ref_acquire takes two locks in this order: ref_table_lock entry->lock while tipc_deleteport takes them in this order: entry->lock (via tipc_port_lock()) ref_table_lock (via tipc_ref_discard()) when the same entry is referenced, we get the above warning. The fix is equally straightforward. Theres no real relation between the entry->lock and the ref_table_lock (they just are needed at the same time), so move the entry->lock aquisition in tipc_ref_acquire down, after we unlock ref_table_lock (this is safe since the ref_table_lock guards changes to the reference table, and we've already claimed a slot there. I've tested the below fix and confirmed that it clears up the lockdep issue Signed-off-by: Neil Horman <nhorman@tuxdriver.com> CC: Allan Stephens <allan.stephens@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/tipc')
-rw-r--r--net/tipc/ref.c26
1 files changed, 16 insertions, 10 deletions
diff --git a/net/tipc/ref.c b/net/tipc/ref.c
index 414fc34b8be..8dea66500cf 100644
--- a/net/tipc/ref.c
+++ b/net/tipc/ref.c
@@ -153,11 +153,11 @@ void tipc_ref_table_stop(void)
u32 tipc_ref_acquire(void *object, spinlock_t **lock)
{
- struct reference *entry;
u32 index;
u32 index_mask;
u32 next_plus_upper;
u32 ref;
+ struct reference *entry = NULL;
if (!object) {
err("Attempt to acquire reference to non-existent object\n");
@@ -175,30 +175,36 @@ u32 tipc_ref_acquire(void *object, spinlock_t **lock)
index = tipc_ref_table.first_free;
entry = &(tipc_ref_table.entries[index]);
index_mask = tipc_ref_table.index_mask;
- /* take lock in case a previous user of entry still holds it */
- spin_lock_bh(&entry->lock);
next_plus_upper = entry->ref;
tipc_ref_table.first_free = next_plus_upper & index_mask;
ref = (next_plus_upper & ~index_mask) + index;
- entry->ref = ref;
- entry->object = object;
- *lock = &entry->lock;
}
else if (tipc_ref_table.init_point < tipc_ref_table.capacity) {
index = tipc_ref_table.init_point++;
entry = &(tipc_ref_table.entries[index]);
spin_lock_init(&entry->lock);
- spin_lock_bh(&entry->lock);
ref = tipc_ref_table.start_mask + index;
- entry->ref = ref;
- entry->object = object;
- *lock = &entry->lock;
}
else {
ref = 0;
}
write_unlock_bh(&ref_table_lock);
+ /*
+ * Grab the lock so no one else can modify this entry
+ * While we assign its ref value & object pointer
+ */
+ if (entry) {
+ spin_lock_bh(&entry->lock);
+ entry->ref = ref;
+ entry->object = object;
+ *lock = &entry->lock;
+ /*
+ * keep it locked, the caller is responsible
+ * for unlocking this when they're done with it
+ */
+ }
+
return ref;
}