Re: Are there u32 atomic bitops? (or dealing w/ i_flags)

From: Al Viro
Date: Mon Dec 17 2012 - 20:57:00 EST

On Mon, Dec 17, 2012 at 05:10:21PM -0800, Andy Lutomirski wrote:
> I want to change inode->i_flags access to be atomic -- there are some
> locking oddities right now, I think, and I want to use a new inode
> flag to signal mtime updates from page_mkwrite. The problem is that
> i_flags is an unsigned int, and making it an unsigned long seems like
> a waste, but there aren't any u32 atomic bitops.

... and atomic accesses cost more. A lot more on some architectures.
FWIW, atomic_t *is* 32bit on 32bit architectures, which still doesn't
make it a good idea.
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