lkml.org 
[lkml]   [2000]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Request for net guru help: waitqueue oops
Hi Petkan,

Thanks for your comment.

On Tue, 3 Oct 2000, Petko Manolov wrote:
> > A driver I'm working on seems to be doing/triggering something related
> > to waitqueues. This causes a perfectly reproducable oops (small mercies!).
> > Since the oops is not happening in my driver, I'm having a hard time
> > figuring out whats going wrong. I suspect a networking guru will take
> > one look and know what I'm doing wrong. Any suggestions please?
>
>
> It seems you're trying to sleep without process context (most likely in
> net_tx_action). It would be more clear if you send that part of the
> code.

Since I don't explictly sleep anywhere, I'm not sure which code fragment
would be useful... (net_tx_action is part of the networking layers). Which
network functions can sleep (netif_rx, netif_stop_queue, netif_wake_queue,
...) ?

After reading the softnet HOWTO, and some of the network drivers, I
was unsure about the netif_stop_queue and netif_wake_queue functions. The
howto indicated that these two should be protected from concurrent
execution by a private lock. Not all the drivers seem to do this. In my
case (although I'm running UP at the moment), I've used a driver global
spinlock, for example:

spinlock_t driver_lock = SPIN_LOCK_UNLOCKED;

int scc72_hard_xmit (struct sk_buff *skb, struct net_device *dev)
{
unsigned long flags;

/* ... */

spin_lock_irqsave (&driver_lock, flags);
netif_stop_queue (dev);
spin_unlock_irqrestore (&driver_lock, flags);

/* ... */
}

/* Example timer callback, to wake the queue */
void scc72_interframewait (unsigned long channel)
{
unsigned long flags;
struct scc72_channel *scc = (struct scc72_channel *) channel;

/* ... */

spin_lock_irqsave (&driver_lock, flags);

/* ... */

if (netif_queue_stopped (scc->dev))
netif_wake_queue (scc->dev);

spin_unlock_irqrestore (&driver_lock, flags);
}

I've just checked my driver, and below is the list of all the external
functions called. Any idea which of these could be trying to sleep?

dev_kfree_skb_any (called from both hard IRQ and non IRQ context)
dev_alloc_skb (called from both hard IRQ and non IRQ context)
del_timer (called from both hard IRQ and non IRQ context)
add_timer (called from both hard IRQ and non IRQ context)
netif_rx (called from IRQ context)
netif_start_queue (called from non hard IRQ context, ex: dev_open)
netif_stop_queue (called from non hard IRQ context, ex: hard_start_xmit)
netif_wake_queue (called from non hard IRQ context, ex: timer callbacks)
netif_queue_stopped (called from non hard IRQ context, ex: timer callbacks)
skb_queue_tail (called from non hard IRQ context, ex: hard_start_xmit)
skb_dequeue (called from both hard IRQ and non IRQ context)
skb_queue_head_init (called from non hard IRQ context, ex: dev_open)

and the standard functions dev_init_buffers, register_netdevice,
copy_from_user, unregister_netdev, etc. called in the standard places.

skb_queue_tail, skb_dequeue and skb_queue_head_init are used to manage
an internal queue of outgoing skb's.

Thanks.
-- Hans




-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:39    [W:0.058 / U:0.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site