Debug: sleeping function called from invalid context at mm/slab.c:2126

[Tony]

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;
}

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