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Date: Sun, 10 Feb 2008 00:50:29 +0100 From: Jarek Poplawski <jarkao2@...il.com> To: David Miller <davem@...emloft.net> Cc: Bernard Pidoux F6BVP <f6bvp@...e.fr>, Ralf Baechle DL5RB <ralf@...ux-mips.org>, Jann Traschewski <jann@....de>, netdev@...r.kernel.org Subject: [PATCH][AX25] af_ax25: remove sock lock in ax25_info_show() 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 <f6bvp@...e.fr> Signed-off-by: Jarek Poplawski <jarkao2@...il.com> --- 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"); } -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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