On Sat, Feb 09, 2008 at 07:44:50PM +0100, Bernard Pidoux F6BVP wrote:
> Hi,
>
> With AX25 patches applied I still get this possible circular locking
> message.
IMHO this warning could happen earlier too...
Thanks,
Jarek P.
-------------->
Subject: [AX25] af_ax25: remove sock lock in ax25_info_show()
This lockdep warning:
> =======================================================
> [ INFO: possible circular locking dependency detected ]
> 2.6.24 #3
> -------------------------------------------------------
> swapper/0 is trying to acquire lock:
> (ax25_list_lock){-+..}, at: [<f91dd3b1>] ax25_destroy_socket+0x171/0x1f0
> [ax25]
>
> but task is already holding lock:
> (slock-AF_AX25){-+..}, at: [<f91dbabc>] ax25_std_heartbeat_expiry+0x1c/0xe0
> [ax25]
>
> which lock already depends on the new lock.
...
shows that ax25_list_lock and slock-AF_AX25 are taken in different
order: ax25_info_show() takes slock (bh_lock_sock(ax25->sk)) while
ax25_list_lock is held, so reversely to other functions. To fix this
the sock lock should be moved to ax25_info_start(), but since it's
only for reading proc info it seems this is not necessary (e.g.
ax25_send_to_raw() does similar reading without this lock too). So,
this patch removes this lock to avoid deadlock possibility.
Reported-by: Bernard Pidoux F6BVP <[EMAIL PROTECTED]>
Signed-off-by: Jarek Poplawski <[EMAIL PROTECTED]>
---
net/ax25/af_ax25.c | 2 --
1 files changed, 0 insertions(+), 2 deletions(-)
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index 94b2b1b..68b5171 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -1924,12 +1924,10 @@ static int ax25_info_show(struct seq_file *seq, void *v)
ax25->paclen);
if (ax25->sk != NULL) {
- bh_lock_sock(ax25->sk);
seq_printf(seq," %d %d %ld\n",
atomic_read(&ax25->sk->sk_wmem_alloc),
atomic_read(&ax25->sk->sk_rmem_alloc),
ax25->sk->sk_socket != NULL ?
SOCK_INODE(ax25->sk->sk_socket)->i_ino : 0L);
- bh_unlock_sock(ax25->sk);
} else {
seq_puts(seq, " * * *\n");
}
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