On Wed, May 16, 2007 at 05:41:01PM -0700, David Miller wrote:
> From: [EMAIL PROTECTED] (Linas Vepstas)
> Date: Wed, 16 May 2007 19:18:02 -0500
>
> > Since this is a long email; let me put a summary up front:
> > I think the RT/premption patches are exposing some sort
> > of race in the ip header handling code. The rest of the
> > note is forensics pointing to this.
>
> skb->head should never ever be NULL.
The stack trace from Owa-san showed a null pointer deref at
ip_hdr(skb)->protocol for an skb passed in via hard_start_xmit()
I dunno, memory corruption?
Tsutomu, can you reproduce this with something similr to the following
patch?
--linas
drivers/net/spider_net.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
Index: linux-2.6.22-rc1/drivers/net/spider_net.c
===================================================================
--- linux-2.6.22-rc1.orig/drivers/net/spider_net.c 2007-05-17
18:31:40.000000000 -0500
+++ linux-2.6.22-rc1/drivers/net/spider_net.c 2007-05-17 18:51:49.000000000
-0500
@@ -720,7 +720,19 @@ spider_net_prepare_tx_descr(struct spide
SPIDER_NET_DESCR_CARDOWNED | SPIDER_NET_DMAC_NOCS;
spin_unlock_irqrestore(&chain->lock, flags);
- if (skb->protocol == htons(ETH_P_IP) && skb->ip_summed ==
CHECKSUM_PARTIAL)
+ if (skb->protocol == htons(ETH_P_IP) && skb->ip_summed ==
CHECKSUM_PARTIAL) {
+ struct iphdr *hp=ip_hdr(skb);
+ if (((unsigned long) hp < 0x100000) ||
+ ((unsigned long)hp > 0xffff000000000000UL)) {
+ printk(KERN_ERROR "spidernet: bad ip header! "
+ "skb=%p ip_hdr=%p head=%p data=%p net=%x\n",
skb, hp,
+ skb->head, skb->data, skb->network_header);
+ int i;
+ unsinged long *s=(unsigned long*) skb;
+ for (i=0; i<20; i++) {
+ printk("%d %lx %lx\n", i, s[2*i],s[2*i+1]);
+ }
+ } else {
switch (ip_hdr(skb)->protocol) {
case IPPROTO_TCP:
hwdescr->dmac_cmd_status |= SPIDER_NET_DMAC_TCP;
@@ -728,6 +740,8 @@ spider_net_prepare_tx_descr(struct spide
case IPPROTO_UDP:
hwdescr->dmac_cmd_status |= SPIDER_NET_DMAC_UDP;
break;
+ }
+ }
}
/* Chain the bus address, so that the DMA engine finds this descr. */
-
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