2.6.31-git5 kernel boot hangs on powerpc

[Sachin Sant]

Tejun Heo wrote:
> Benjamin Herrenschmidt wrote:
>   
>>> --- Exception: 301 at .memset+0x60/0xfc
>>>     LR = .pcpu_alloc+0x718/0x8fc
>>>       
>> So it's memsetting something that causes it to hash_page(), ie, faulting
>> in pages (vmalloc space ?) so far nothing obviously wrong....
>>     
>
> It's probably memset() call near the end of pcpu_populate_chunk()
> where percpu allocator clears the allocated areas before returning to
> user.  I don't think the first chunk is causing the problem as they're
> all in the linear mapped area.  From the second chunk on, they're on
> vmalloc area and very near to the top of it, so that might be exposing
> a hidden problem in paging code?  BTW, for some reason, the problem is
> not reproducible on my powerstation.
>
> Sachin, can you please apply the attached patch on top of the current
> linus tree, reproduce the hang and report full kernel log?  Let's see
> which address is causing the problem.
>   
Here is the dmesg log captured with the debug patch.

Some of the debug messages related to PERCPU

<6>PERCPU: Embedded 2 pages/cpu @c000000001100000 s97160 r0 d33912 u524288
<6>pcpu-alloc: s97160 r0 d33912 u524288 alloc=1*1048576
<6>pcpu-alloc: [0] 0 1
<4>PERCPU: initialized 19 slots [c000000001120200,c000000001120330)
<4>PERCPU: chunk 0 relocating -1 -> 13 c000000001120380 <c000000001120380:c000000001120380>
<4>PERCPU: relocated <c0000000011202d0:c0000000011202d0>

<4>PERCPU: chunk 0 relocating 13 -> 12 c000000001120380 <c0000000011202d0:c0000000011202d0>
<4>PERCPU: relocated <c0000000011202c0:c0000000011202c0>

<4>PERCPU: chunk 0 relocating 12 -> 11 c000000001120380 <c0000000011202c0:c0000000011202c0>
<4>PERCPU: relocated <c0000000011202b0:c0000000011202b0>

<6>ehea: eth0: Physical port up
<6>ehea: External switch port is backup port
<7>irq: irq 33540 on host null mapped to virtual irq 260
<6>NET: Registered protocol family 10
<4>PERCPU: chunk 0 relocating 11 -> 10 c000000001120380 <c0000000011202b0:c0000000011202b0>
<4>PERCPU: relocated <c0000000011202a0:c0000000011202a0>
<4>PERCPU: chunk 0 relocating 10 -> 9 c000000001120380 <c0000000011202a0:c0000000011202a0>
<4>PERCPU: relocated <c000000001120290:c000000001120290>
<4>PERCPU: chunk 1 relocating -1 -> 18 c0000000db70fb00 <c0000000db70fb00:c0000000db70fb00>
<4>PERCPU: relocated <c000000001120320:c000000001120320>
<4>PERCPU: chunk 1 relocating 18 -> 16 c0000000db70fb00 <c000000001120320:c000000001120320>
<4>PERCPU: relocated <c000000001120300:c000000001120300>
<4>PERCPU: chunk 1, alloc pages [0,1)
<4>PERCPU: chunk 1, map pages [0,1)
<4>PERCPU: map 0xd00007fffff00000, 1 pages 53544
<4>PERCPU: map 0xd00007fffff80000, 1 pages 53545
<4>PERCPU: chunk 1, will clear 4096b/unit d00007fffff00000 d00007fffff80000
<3>INFO: RCU detected CPU 0 stall (t=1000 jiffies)

Thanks
-Sachin



-- 

---------------------------------
Sachin Sant
IBM Linux Technology Center
India Systems and Technology Labs
Bangalore, India
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