From: Ingo Molnar <mingo@elte.hu>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>, linux-kernel@vger.kernel.org
Subject: Re: [lock validator] inet6_destroy_sock(): soft-safe -> soft-unsafe lock dependency
Date: Thu, 2 Feb 2006 12:27:31 +0100 [thread overview]
Message-ID: <20060202112731.GA11603@elte.hu> (raw)
In-Reply-To: <20060202105429.GA4895@elte.hu>
* Ingo Molnar <mingo@elte.hu> wrote:
> hm, i got a new one:
>
> ============================================
> [ BUG: circular locking deadlock detected! ]
> --------------------------------------------
> sshd/28997 is trying to acquire lock:
> (&sk->sk_lock.slock){-+}, at: [<c0c6be28>] packet_rcv+0xbf/0x34b
>
> but task is already holding lock:
> (&dev->xmit_lock){-+}, at: [<c0bb04ec>] qdisc_restart+0x46/0x207
>
> which lock already depends on the new lock,
> which could lead to circular deadlocks!
>
> the dependency chain (in reverse order) is:
> -> #2 (&dev->xmit_lock){-+}: [<c0bb04ec>] qdisc_restart+0x46/0x207
> -> #1 (&dev->queue_lock){-+}: [<c0b98137>] dev_queue_xmit+0xc3/0x21e
> -> #0 (&sk->sk_lock.slock){-+}: [<c0c6be28>] packet_rcv+0xbf/0x34b
i think this might be a false positive, caused by my (ill-advised)
change below? [i did the change to clean up an unlock ordering
assymetry, but apparently i thus also introduced the xmit_lock ->
queue_lock dependency.]
Ingo
Index: linux/net/sched/sch_generic.c
===================================================================
--- linux.orig/net/sched/sch_generic.c
+++ linux/net/sched/sch_generic.c
@@ -98,6 +98,8 @@ int qdisc_restart(struct net_device *dev
/* Dequeue packet */
if ((skb = q->dequeue(q)) != NULL) {
unsigned nolock = (dev->features & NETIF_F_LLTX);
+ /* release queue */
+ spin_unlock(&dev->queue_lock);
/*
* When the driver has LLTX set it does its own locking
* in start_xmit. No need to add additional overhead by
@@ -121,9 +123,11 @@ int qdisc_restart(struct net_device *dev
kfree_skb(skb);
if (net_ratelimit())
printk(KERN_DEBUG "Dead loop on netdevice %s, fix it urgently!\n", dev->name);
+ spin_lock(&dev->queue_lock);
return -1;
}
__get_cpu_var(netdev_rx_stat).cpu_collision++;
+ spin_lock(&dev->queue_lock);
goto requeue;
}
/* Remember that the driver is grabbed by us. */
@@ -131,8 +135,6 @@ int qdisc_restart(struct net_device *dev
}
{
- /* And release queue */
- spin_unlock(&dev->queue_lock);
if (!netif_queue_stopped(dev)) {
int ret;
next prev parent reply other threads:[~2006-02-02 11:29 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-27 0:18 [lock validator] net/ipv4/fib_hash.c: illegal {enabled-softirqs} -> {used-in-softirq} usage? Ingo Molnar
2006-01-27 1:41 ` Herbert Xu
2006-01-28 15:22 ` [lock validator] inet6_destroy_sock(): soft-safe -> soft-unsafe lock dependency Ingo Molnar
2006-01-28 15:44 ` Ingo Molnar
2006-01-31 10:27 ` Herbert Xu
2006-01-31 10:43 ` David S. Miller
2006-01-31 11:21 ` Ingo Molnar
2006-02-01 13:32 ` Ingo Molnar
2006-02-01 20:26 ` Herbert Xu
2006-02-02 7:46 ` Ingo Molnar
2006-02-02 8:48 ` Herbert Xu
2006-02-02 9:04 ` David S. Miller
2006-02-02 10:54 ` Ingo Molnar
2006-02-02 11:27 ` Ingo Molnar [this message]
2006-02-02 12:19 ` Herbert Xu
2006-02-02 12:17 ` Herbert Xu
2006-02-02 13:54 ` Ingo Molnar
2006-01-31 21:24 ` Ingo Molnar
2006-01-31 22:06 ` Herbert Xu
2006-02-01 10:42 ` Herbert Xu
2006-02-01 11:13 ` Ingo Molnar
2006-02-03 1:01 ` David S. Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20060202112731.GA11603@elte.hu \
--to=mingo@elte.hu \
--cc=davem@davemloft.net \
--cc=herbert@gondor.apana.org.au \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).