Re: [PATCH -v6 2/2] Updating ctime and mtime for memory-mappedfiles

[Linus Torvalds]

On Sat, 19 Jan 2008, Anton Salikhmetov wrote:
> 
> Before using pte_wrprotect() the vma_wrprotect() routine uses the
> pte_offset_map_lock() macro to get the PTE and to acquire the ptl
> spinlock. Why did you say that this code was not SMP-safe? It should
> be atomic, I think.

It's atomic WITH RESPECT TO OTHER PEOPLE WHO GET THE LOCK.

Guess how much another x86 CPU cares when it sets the accessed bit in 
hardware?

> The POSIX standard requires the ctime and mtime stamps to be updated
> not later than at the second call to msync() with the MS_ASYNC flag.

.. and that is no excuse for bad code.

			Linus
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