I'm writing a net_device driver. I want to send a packet when the timer
is out. I get the following warning. It seems that I should not call
alloc_skb. Can anyone tell me how to get rid of this? Thanks in advance.
Nov 10 08:54:33 localhost kernel: Debug: sleeping function called from
invalid context at mm/slab.c:2126
Nov 10 08:54:33 localhost kernel: in_atomic():1, irqs_disabled():0
Nov 10 08:54:33 localhost kernel: [<c015c27e>] kmem_cache_alloc+0x3c/0x49
Nov 10 08:54:33 localhost kernel: [<c0301b02>] alloc_skb+0x14/0xc1
Nov 10 08:54:33 localhost kernel: [<cc8d3056>] rcp_match+0x0/0x1ef [rd]
Nov 10 08:54:33 localhost kernel: [<cc8d3077>] rcp_match+0x21/0x1ef [rd]
Nov 10 08:54:33 localhost kernel: [<c012c9ae>] cascade+0x21/0x3b
Nov 10 08:54:33 localhost kernel: [<cc8d3056>] rcp_match+0x0/0x1ef [rd]
Nov 10 08:54:33 localhost kernel: [<c012cf73>]
run_timer_softirq+0x10b/0x472
Nov 10 08:54:33 localhost kernel: [<c0103c0e>] common_interrupt+0x1a/0x20
Nov 10 08:54:33 localhost kernel: [<c01282de>] __do_softirq+0x3e/0x8a
Nov 10 08:54:33 localhost kernel: [<c0105c29>] do_softirq+0x3e/0x42
Nov 10 08:54:33 localhost kernel: =======================
Nov 10 08:54:33 localhost kernel: [<c0105b24>] do_IRQ+0x51/0x82
Nov 10 08:54:33 localhost kernel: [<c0105b24>] do_IRQ+0x51/0x82
Nov 10 08:54:33 localhost kernel: [<c0103c0e>] common_interrupt+0x1a/0x20
Nov 10 08:54:33 localhost kernel: [<c010101a>] default_idle+0x0/0x29
Nov 10 08:54:33 localhost kernel: [<c0101040>] default_idle+0x26/0x29
Nov 10 08:54:33 localhost kernel: [<c01010a6>] cpu_idle+0x34/0x4c
Nov 10 08:54:33 localhost kernel: [<c042472a>] start_kernel+0x15f/0x1b9
Nov 10 08:54:33 localhost kernel: [<c04242fe>] unknown_bootoption+0x0/0x1cd
the timeout function is as below:
static void rcp_match(unsigned long dummy)
{
struct sk_buff *skb;
struct net_device *dev;
struct rcpchdr *h;
struct rcpopt *o;
int res;
static uint8_t broadcast[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
#if DEBUG_LEVEL < 1
printk(KERN_WARNING "-> rcp_match\n");
#endif
if (rcp_match_count++ >= RCP_MATCH_RETRY)
goto stop;
skb = alloc_skb(512, GFP_KERNEL);
if (skb == NULL) {
printk(KERN_WARNING "rcp_match: not enough sk_buff\n");
goto stop;
}
dev = dev_get_by_name("eth0");
if (dev == NULL) {
printk(KERN_WARNING "rcp_match: net_device not found (%s)\n",
"eth0");
goto stop;
}
skb_reserve(skb, dev->hard_header_len);
h = (struct rcpchdr *)skb_put(skb, sizeof (struct rcpchdr));
h->h_type = RCPC_TYPE_QUERY;
h->h_index = RCPC_INDEX_ALL;
o = (struct rcpopt *)skb_put(skb, sizeof (struct rcpopt));
memset(o, 8, sizeof(struct rcpopt));
skb->protocol = htons(ETH_P_RADIO_CONTROL);
skb->nh.raw = skb->data;
skb->dev = dev;
res = dev->hard_header(skb, dev, ETH_P_RADIO_CONTROL, broadcast,
NULL, skb->len);
if (res < 0) {
dev_kfree_skb(skb);
dev_put(dev);
return;
}
res = dev_queue_xmit(skb);
dev_put(dev);
rcp_match_timer.expires = jiffies + RCP_MATCH_TIMEO;
add_timer(&rcp_match_timer);
return;
stop:
del_timer_sync(&rcp_match_timer);
rcp_match_count = 0;
return;
}
> I'm writing a net_device driver. I want to send a packet when the timer
> is out. I get the following warning. It seems that I should not call
> alloc_skb. Can anyone tell me how to get rid of this? Thanks in advance.
>
You are calling alloc_skb which in turn calls kmem_cache_alloc in interrupt context where things can't sleep and kmem_cache_alloc can sleep. The reason for this is that you are passing GFP_KERNEL to alloc_skb. Try passing GFP_ATOMIC instead.
Other alternative is to may be use a precreated pool of skbs - may be this can be done in driver init function or any other safe context. But I don't know how much feasible that is in your situation.
HTH
Parag
Parag Warudkar wrote:
>>I'm writing a net_device driver. I want to send a packet when the timer
>>is out. I get the following warning. It seems that I should not call
>>alloc_skb. Can anyone tell me how to get rid of this? Thanks in advance.
>>
>
>
> You are calling alloc_skb which in turn calls kmem_cache_alloc in interrupt context where things can't sleep and kmem_cache_alloc can sleep. The reason for this is that you are passing GFP_KERNEL to alloc_skb. Try passing GFP_ATOMIC instead.
>
> Other alternative is to may be use a precreated pool of skbs - may be this can be done in driver init function or any other safe context. But I don't know how much feasible that is in your situation.
>
> HTH
> Parag
>
>
>
Thanks a lot. Another question.
My interface is a virtual interface which represent a radio connected to
the host using ethernet NIC. I designed my own L2 protocol on top of
802.3, which must be used, since the radio and the host are connected by
ethernet.
Now, my radio_hard_header will only add my L2 header, and my
radio_hard_start_xmit will do (simplified):
1) ajust the headroom space
hh_len = LL_RESERVED_SPACE(bdev);
if (unlikely(skb_headroom(skb) < hh_len && bdev->hard_header)) {
struct sk_buff *skb2;
skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
if (skb2 == NULL) {
stats->tx_dropped++;
dev_kfree_skb(skb);
return 0;
}
if (skb->sk)
skb_set_owner_w(skb2, skb->sk);
dev_kfree_skb(skb);
skb = skb2;
}
2) call eth0->hard_header
3) skb->dev = eth0
return dev_queue_xmit()
The problem is when system try to retransmit the packet, I add another
ethernet header mistakenly.
I have two question:
1) I do not modify the skb passed to hard_start_xmit if
skb_realloc_headroom is executed. only in this case the retransmission
runs well. Is my understanding right?
2) Should I do this way or add the ethernet header in my
radio_hard_header? If I choose the later, the problem will be how should
I handle it when eth_hard_header return a negative number, when ARP is
needed.
Thx
On Nov 9, 2005, at 10:42 PM, Tony wrote:
> Thanks a lot. Another question.
>
I don't know the answer to that. You might find some help on the
linux network development list - try asking
[email protected]
Parag