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[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(), and there would
be still problem with breaking ax25_list_lock (it seems this "proper"
order isn't optimal yet). 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 sock lock to avoid deadlock possibility; there
is also used sock_i_ino() function, which reads sk_socket under proper
read lock. Additionally printf format of this i_ino is changed to %lu.

Reported-by: Bernard Pidoux F6BVP <f6bvp@free.fr>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jarek Poplawski 2008-02-11 21:24:56 -08:00 committed by David S. Miller
parent 8315f5d80a
commit 1105b5d1d4
1 changed files with 2 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
net/ax25/af_ax25.c
View File

@ -1928,12 +1928,10 @@ 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",
seq_printf(seq, " %d %d %lu\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);
sock_i_ino(ax25->sk));
} else {
seq_puts(seq, " * * *\n");
}