Re: Do I need spin_lock before pgd/pmd/pte_offset?

[Timur Tabi <timur.tabi@ammasso.com>]

Ed L Cashin wrote:

> The normal order of lock acquisition is first to get the mmap
> semaphore (at which point you may sleep) and then to get the page
> table lock.

So you're saying I need to use

	down_read(&current->mm->mmap_sem);
	...
	up_read(&current->mm->mmap_sem);

In addition to the spinlocks?

> A good reference for the proceedure you're implementing is follow_page
> in mm/memory.c.  Note that it's called with the page_table_lock held.

I'm looking at follow_page() in 2.6.6, and I don't see any spinlock or 
semaphore code.  The code in RedHat 9.0 is also similar in this respect.

> No, the page table lock allows you to see a consistent view of the
> page tables while you hold it.  

Is "&current->mm->page_table_lock" the right parameter to use in this case?

--
Timur Tabi
Staff Software Engineer
timur.tabi@ammasso.com

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