On Friday, 13 of June 2008, Zhang, Yanmin wrote:
quoted text
> With kernel 2.6.26-rc5 and a git kernel just between rc4 and rc5, my
> kernel panic on my Montvale machine when I did an initial specweb2005
> testing between 2 machines.

I have created the Bugzilla entry at
http://bugzilla.kernel.org/show_bug.cgi?id=10908
for this bug.  Can you add yourself to the CC list in there, please?

quoted text
> Below is the log.
> 
> LOGIN: Unable to handle kernel NULL pointer dereference (address 0000000000000000)
> Thread-7266[13494]: Oops 8804682956800 [1]
> Modules linked in:
> 
> Pid: 13494, CPU 0, comm:          Thread-7266
> psr : 0000101008026018 ifs : 800000000000050e ip  : [<a00000010087a4b0>]    Not tainted (2.6.26-rc4git)
> ip is at tcp_rcv_established+0x1450/0x16e0
> unat: 0000000000000000 pfs : 000000000000050e rsc : 0000000000000003
> rnat: 0000000000000000 bsps: 0000000000000000 pr  : 000000000059656b
> ldrs: 0000000000000000 ccv : 0000000000000000 fpsr: 0009804c8a70033f
> csd : 0000000000000000 ssd : 0000000000000000
> b0  : a00000010087a410 b6  : a0000001004c7ac0 b7  : a0000001004c64e0
> f6  : 000000000000000000000 f7  : 1003e0000000000000b80
> f8  : 10000821f080500000000 f9  : 1003efffffffffffffa58
> f10 : 1003edbb7db5f6be58df8 f11 : 1003e0000000000000015
> r1  : a0000001010cce90 r2  : e0000003d4530c40 r3  : 0000000000000105
> r8  : e000000402533d68 r9  : e000000402533a80 r10 : e000000402533bfc
> r11 : 0000000000000004 r12 : e0000003d4537df0 r13 : e0000003d4530000
> r14 : 0000000000000000 r15 : e000000401fca180 r16 : e0000003d4530c68
> r17 : e000000402572238 r18 : 00000000000000ff r19 : a0000001012c6630
> r20 : e0000003d4530c68 r21 : e000000401fca480 r22 : e000000402572658
> r23 : e000000402572240 r24 : a0000001012c4e04 r25 : 0000000000000003
> r26 : e000000401fca4a8 r27 : e000000402572660 r28 : e00000040a2d2a00
> r29 : e00000040a6f83a8 r30 : e00000040a6f8300 r31 : 000000000000000a
> 
> Call Trace:
>  [<a000000100014de0>] show_stack+0x40/0xa0
>                                 sp=e0000003d45379c0 bsp=e0000003d4531440
>  [<a0000001000156f0>] show_regs+0x850/0x8a0
>                                 sp=e0000003d4537b90 bsp=e0000003d45313e0
>  [<a000000100038d10>] die+0x230/0x360
>                                 sp=e0000003d4537b90 bsp=e0000003d4531398
>  [<a00000010005cec0>] ia64_do_page_fault+0x8e0/0xa40
>                                 sp=e0000003d4537b90 bsp=e0000003d4531348
>  [<a00000010000b120>] ia64_leave_kernel+0x0/0x280
>                                 sp=e0000003d4537c20 bsp=e0000003d4531348
>  [<a00000010087a4b0>] tcp_rcv_established+0x1450/0x16e0
>                                 sp=e0000003d4537df0 bsp=e0000003d45312d8
>  [<a000000100888370>] tcp_v4_do_rcv+0x70/0x500
>                                 sp=e0000003d4537df0 bsp=e0000003d4531298
>  [<a00000010088cd30>] tcp_v4_rcv+0xfb0/0x1060
>                                 sp=e0000003d4537e00 bsp=e0000003d4531248
> 
> 
> 
> As a matter of fact, kernel paniced at statement
> "queue->rskq_accept_tail->dl_next = req" in function reqsk_queue_add, because
> queue->rskq_accept_tail is NULL. The call chain is:
> tcp_rcv_established => inet_csk_reqsk_queue_add => reqsk_queue_add.
> 
> As I was running an initial specweb2005(configured 3500 sessions) testing between
> 2 machines, there were lots of failure and many network connections were
> reestablished during the testing.
> 
> In function tcp_v4_rcv, bh_lock_sock_nested(sk) (a kind of spinlock) is used to
> avoid race. But inet_csk_accept uses lock_sock(sk) (a kind of sleeper). Although
> lock_sock also accesses sk->sk_lock.slock, it looks like there is a race.

Thanks,
Rafael
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