Re: [PATCH] mmap.2: MAP_FIXED is okay if the address range has been reserved

[Michal Hocko]

On Fri 13-04-18 08:43:27, Michael Kerrisk wrote:
[...]
> So, you mean remove this entire paragraph:
> 
>               For cases in which the specified memory region has not been
>               reserved using an existing mapping,  newer  kernels  (Linux
>               4.17  and later) provide an option MAP_FIXED_NOREPLACE that
>               should be used instead; older kernels require the caller to
>               use addr as a hint (without MAP_FIXED) and take appropriate
>               action if the kernel places the new mapping at a  different
>               address.
> 
> It seems like some version of the first half of the paragraph is worth 
> keeping, though, so as to point the reader in the direction of a remedy.
> How about replacing that text with the following:
> 
>               Since  Linux 4.17, the MAP_FIXED_NOREPLACE flag can be used
>               in a multithreaded program to avoid  the  hazard  described
>               above.

Yes, that sounds reasonable to me.

-- 
Michal Hocko
SUSE Labs