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xen-devel
Re: [Xen-devel] [PATCH] atomic_read
On Mar 11, 2005, at 10:53 AM, Keir Fraser wrote:
On 11 Mar 2005, at 14:57, Hollis Blanchard wrote:
Hi, I noticed that include/xen/sched.h uses _atomic_*() in a couple
places, while all other Xen code uses atomic_*(). In general I think
functions prefixed with an underscore are not part of the public
interface...
This patch should be safe since atomic_*() just use volatile and
_atomic_*() do not.
Side note: the Xen copy of atomic.h appears to be a little out of
date with respect to the Linux 2.6.11 version, in which _atomic_*()
is no longer present (only atomic_*() are).
The xen _atomic_* functions aren't like the old Linux ones -- they
don't take a pointer to the atomic_t. We use this in the scheduler to
produce better-quality code. The patch you sent won't compile because
e.g., atomic_set and _atomic_set take different type parameters.
Ahh... I assumed asm-x86/atomic.h was simply out of date, but I see now
that you've modified it yourself. So _atomic_* should now be considered
part of the arch->common interface? Further, it should actually *not*
be an atomic access at all? Of course it will be faster
("better-quality") code if it's not assumed to be an atomic access...
in which case isn't the naming a little misleading?
I noticed this problem because linux/include/asm-ppc64/atomic.h doesn't
have _atomic_* functions. I guess this means I will need to implement
my own non-atomic _atomic_* functions?
--
Hollis Blanchard
IBM Linux Technology Center
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