Re: [PATCH 7/9] mm: split page table lock

[Andrew Morton]

Andrew Morton <akpm@xxxxxxxx> wrote:
>
>  Hugh Dickins <hugh@xxxxxxxxxxx> wrote:
>  >
>  > In this implementation, the spinlock is tucked inside the struct page of
>  >  the page table page: with a BUILD_BUG_ON in case it overflows - which it
>  >  would in the case of 32-bit PA-RISC with spinlock debugging enabled.
> 
>  eh?   It's going to overflow an unsigned long on x86 too:

Ah, I think I see what you've done: assume that .index, .lru and .virtual
are unused on pagetable pages, so we can just overwrite them.

ick.  I think I prefer the union, although it'll make struct page bigger
for CONFIG_PREEMPT+CONFIG_SMP+NR_CPUS>=4.    hmm.


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