2014-12-18 1:10 GMT+09:00 Christoph Lameter <cl@xxxxxxxxx>:
> On Wed, 17 Dec 2014, Joonsoo Kim wrote:
>
>> + do {
>> + tid = this_cpu_read(s->cpu_slab->tid);
>> + c = this_cpu_ptr(s->cpu_slab);
>> + } while (IS_ENABLED(CONFIG_PREEMPT) && unlikely(tid != c->tid));
>
>
> Assembly code produced is a bit weird. I think the compiler undoes what
> you wanted to do:
I checked my compiled code and it seems to be no problem.
gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2
Thanks.
> 46fb: 49 8b 1e mov (%r14),%rbx rbx = c =s->cpu_slab?
> 46fe: 65 4c 8b 6b 08 mov %gs:0x8(%rbx),%r13 r13 = tid
> 4703: e8 00 00 00 00 callq 4708 <kmem_cache_alloc+0x48> ??
> 4708: 89 c0 mov %eax,%eax ??
> 470a: 48 03 1c c5 00 00 00 add 0x0(,%rax,8),%rbx ??
> 4711: 00
> 4712: 4c 3b 6b 08 cmp 0x8(%rbx),%r13 tid == c->tid
> 4716: 49 89 d8 mov %rbx,%r8
> 4719: 75 e0 jne 46fb <kmem_cache_alloc+0x3b>
>
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