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Date: Sat, 26 Mar 2011 14:30:33 -0500 (CDT)
From: Christoph Lameter <cl@linux.com>
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To: Eric Dumazet <eric.dumazet@gmail.com>
cc: Ingo Molnar <mingo@elte.hu>, Pekka Enberg <penberg@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, torvalds@linux-foundation.org,
        akpm@linux-foundation.org, tj@kernel.org, npiggin@kernel.dk,
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Subject: Re: [PATCH] slub: Disable the lockless allocator
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Indeed I can reproduce it easily.
With a few printk's this shows that alloc_percpu() returns a wrong
address which is the cause of all of this:

logs:

Memory: 1011444k/1048564k available (11622k kernel code, 452k absent,
36668k reserved, 6270k data, 1028k init)
alloc_kmem_cache_cpus kmem_cache_node = ffff88003ffcf000
alloc_kmem_cache_cpus kmem_cache = ffff88003ffcf020

This means that the cpu_slab is not a percpu pointer.

Now the first allocation attempt:

Slab kmem_cache cpu_slab=ffff88003ffcf020 freelist=ffff88003f8020c0
BUG: unable to handle kernel paging request at ffff87ffc1fdc020
IP: [<ffffffff812c3852>] this_cpu_cmpxchg16b_emu+0x2/0x1c

Tejun: Whats going on there? I should be getting offsets into the per cpu
area and not kernel addresses.

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