Lee Schermerhorn wrote:
> I looked around on the MLs for mention of this, but didn't find anything
> that appeared to match.
>
> Platform: HP rx8620 - 16-cpu/32GB/4-node ia64 [Madison]
>
> 2.6.23-rc7-mm1 broken out -- panic occurs when git-sched.patch pushed:
>
> Unable to handle kernel NULL pointer dereference (address 0000000000000000)
> swapper[0]: Oops 8813272891392 [1]
> Modules linked in: scsi_wait_scan ehci_hcd ohci_hcd uhci_hcd usbcore
>
> Pid: 0, CPU 14, comm: swapper
> psr : 0000101008522030 ifs : 8000000000000002 ip : [<a0000001003014e0>]
> Not tainted
> ip is at rb_next+0x0/0x140
> unat: 0000000000000000 pfs : 0000000000000308 rsc : 0000000000000003
> rnat: 8000000000000012 bsps: 000000000001003e pr : 6609a840599519a5
> ldrs: 0000000000000000 ccv : 0000000000000002 fpsr: 0009804c8a70433f
> csd : 0000000000000000 ssd : 0000000000000000
> b0 : a000000100078dc0 b6 : a000000100074a40 b7 : a000000100078e00
> f6 : 1003e0000000000000000 f7 : 1003e0000000000400000
> f8 : 1003e000000002aaaaaab f9 : 1003e0000000d43798a2b
> f10 : 1003e35e9970b967dd8b9 f11 : 1003e0000000000000002
> r1 : a000000100bc0920 r2 : e0000760000577f0 r3 : e000076000057f10
> r8 : fffffffffffffff0 r9 : 0000000000000002 r10 : e000076000057780
> r11 : 0000000000000000 r12 : e00007004160fe10 r13 : e000070041608000
> r14 : 0000000000000000 r15 : 000000000000000e r16 : 00000007f6c30a22
> r17 : e000070041608040 r18 : a0000001008383a8 r19 : a000000100078e00
> r20 : e000076000055bb8 r21 : e000076000055bb0 r22 : e000076000057ed0
> r23 : 00000000000f4240 r24 : a0000001009e0440 r25 : e000070041608bb4
> r26 : 0000000000000000 r27 : 0000000000000000 r28 : e000076000057f80
> r29 : 00000000000002e7 r30 : 0000000000000000 r31 : e000076000057780
>
> Call Trace:
> [<a000000100014f60>] show_stack+0x80/0xa0
> sp=e00007004160f9e0 bsp=e000070041609008
> [<a000000100015bf0>] show_regs+0x870/0x8a0
> sp=e00007004160fbb0 bsp=e000070041608fa8
> [<a00000010003d170>] die+0x190/0x300
> sp=e00007004160fbb0 bsp=e000070041608f60
> [<a000000100071bc0>] ia64_do_page_fault+0x780/0xa80
> sp=e00007004160fbb0 bsp=e000070041608f08
> [<a00000010000b5c0>] ia64_leave_kernel+0x0/0x270
> sp=e00007004160fc40 bsp=e000070041608f08
> [<a0000001003014e0>] rb_next+0x0/0x140
> sp=e00007004160fe10 bsp=e000070041608ef8
> [<a000000100078dc0>] __dequeue_entity+0x80/0xc0
> sp=e00007004160fe10 bsp=e000070041608ec8
> [<a000000100078e60>] pick_next_task_fair+0x60/0x180
> sp=e00007004160fe10 bsp=e000070041608e98
> [<a0000001006a5880>] schedule+0x340/0x19c0
> sp=e00007004160fe10 bsp=e000070041608cc0
> [<a000000100014cb0>] cpu_idle+0x290/0x3e0
> sp=e00007004160fe30 bsp=e000070041608c50
> [<a000000100066020>] start_secondary+0x380/0x5a0
> sp=e00007004160fe30 bsp=e000070041608c00
> [<a0000001006abca0>] __kprobes_text_end+0x6c0/0x6f0
> sp=e00007004160fe30 bsp=e000070041608c00
>
>
> Taking a quick look at [__]{en|de|queue_entity() and the functions they call,
> I see something suspicious in set_leftmost() in sched_fair.c:
>
> static inline void
> set_leftmost(struct cfs_rq *cfs_rq, struct rb_node *leftmost)
> {
> struct sched_entity *se;
>
> cfs_rq->rb_leftmost = leftmost;
> if (leftmost)
> se = rb_entry(leftmost, struct sched_entity, run_node);
> }
>
> Missing code? corrupt patch?
>
> config available on request, but there doesn't seem to be much in the way
> of scheduler config option. A few that might apply:
>
> SCHED_SMT is not set
> SCHED_DEBUG=y
> SCHEDSTATS=y
>
>
> Regards,
> Lee Schermerhorn
>
Exactly same call trace is produced over IA64 Madison (up to 9M cache) with 8
cpu's.
--
Thanks & Regards,
Kamalesh Babulal,
Linux Technology Center,
IBM, ISTL.
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