2.6.11 oops in skb_drop_fraglist

[Chuck Lever]

testing NFS client workloads on a dual Pentium-III system running 2.6.11 
with some NFS patches.  i hit this oops while doing simple-minded ftps 
and tars.

the system locks up once or twice a day under this workload.  this is 
the first time i had the console and captured the oops output.


Unable to handle kernel NULL pointer dereference at virtual address 00000001
 printing eip:
c02fc752
*pde = 00000000
Oops: 0000 [#1]
SMP
CPU:    0
EIP:    0060:[<c02fc752>]    Not tainted VLI
EFLAGS: 00010202   (2.6.11-CITI_NFS4_ALL-1)
EIP is at skb_drop_fraglist+0x22/0x50
eax: f6fe26e0   ebx: 00000001   ecx: f6fe26e0   edx: 00000001
esi: f6f29240   edi: 00000004   ebp: f697ed24   esp: c04cadd8
ds: 007b   es: 007b   ss: 0068
Process swapper (pid: 0, threadinfo=c04ca000 task=c03efb60)
Stack: 00000001 c02fc7fa f6f29240 f697ecc0 c02fc838 00000000 c02fc8ba 
ccbf2ab0
       00000b50 c0326a16 f6f87740 f6f29240 f6f29240 c0321c4a 00000020 
f6f87778
       f6f87740 f697ecc0 f69d1560 00625a79 c04cae6c 00000000 00000012 
f697ecc0
Call Trace:
 [<c02fc7fa>] skb_release_data+0x5a/0x90
 [<c02fc838>] kfree_skbmem+0x8/0x20
 [<c02fc8ba>] __kfree_skb+0x6a/0xf0
 [<c0326a16>] tcp_transmit_skb+0x406/0x720
 [<c0321c4a>] tcp_clean_rtx_queue+0x17a/0x410
 [<c0322566>] tcp_ack+0xf6/0x580
 [<c03250d9>] tcp_rcv_established+0x409/0x7f0
 [<c0102fa0>] apic_timer_interrupt+0x1c/0x24
 [<c032d8b0>] tcp_v4_do_rcv+0x110/0x120
 [<c032df7f>] tcp_v4_rcv+0x6bf/0x940
 [<c0313212>] ip_local_deliver+0xc2/0x1f0
 [<c0313676>] ip_rcv+0x336/0x450
 [<c02fc591>] alloc_skb+0x41/0xf0
 [<c0302736>] netif_receive_skb+0x136/0x1a0
 [<c026ca9e>] e1000_clean_rx_irq+0x15e/0x4a0
 [<c02fc8ba>] __kfree_skb+0x6a/0xf0
 [<c026c6da>] e1000_clean+0xba/0xf0
 [<c030292f>] net_rx_action+0x6f/0x100
 [<c011d209>] __do_softirq+0xb9/0xd0
 [<c01048aa>] do_softirq+0x4a/0x60

c02fc730:       53                      push   %ebx
c02fc731:       8b 80 94 00 00 00       mov    0x94(%eax),%eax
c02fc737:       8b 58 0c                mov    0xc(%eax),%ebx
c02fc73a:       c7 40 0c 00 00 00 00    movl   $0x0,0xc(%eax)
c02fc741:       eb 0d                   jmp    c02fc750 
<skb_drop_fraglist+0x20>
c02fc743:       90                      nop
c02fc744:       90                      nop
c02fc745:       90                      nop
c02fc746:       90                      nop
c02fc747:       90                      nop
c02fc748:       90                      nop
c02fc749:       90                      nop
c02fc74a:       90                      nop
c02fc74b:       90                      nop
c02fc74c:       90                      nop
c02fc74d:       90                      nop
c02fc74e:       90                      nop
c02fc74f:       90                      nop
c02fc750:       89 da                   mov    %ebx,%edx
c02fc752:       8b 1b                   mov    (%ebx),%ebx
c02fc754:       8b 82 84 00 00 00       mov    0x84(%edx),%eax
c02fc75a:       48                      dec    %eax
c02fc75b:       75 13                   jne    c02fc770 
<skb_drop_fraglist+0x40>
c02fc75d:       f0 83 44 24 00 00       lock addl $0x0,0x0(%esp,1)
c02fc763:       89 d0                   mov    %edx,%eax
c02fc765:       e8 e6 00 00 00          call   c02fc850 <__kfree_skb>
c02fc76a:       85 db                   test   %ebx,%ebx
c02fc76c:       75 e2                   jne    c02fc750 
<skb_drop_fraglist+0x20>
c02fc76e:       5b                      pop    %ebx
c02fc76f:       c3                      ret
c02fc770:       f0 ff 8a 84 00 00 00    lock decl 0x84(%edx)
c02fc777:       0f 94 c0                sete   %al
c02fc77a:       84 c0                   test   %al,%al
c02fc77c:       74 ec                   je     c02fc76a 
<skb_drop_fraglist+0x3a>
c02fc77e:       eb e3                   jmp    c02fc763 
<skb_drop_fraglist+0x33>



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