Messages in this thread | | | From | Linus Torvalds <> | Date | Tue, 31 Jan 2017 13:41:17 -0800 | Subject | Re: [GIT PULL] percpu fix for v4.10-rc6 |
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On Tue, Jan 31, 2017 at 1:32 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > > I've pulled this, but I really think it's papering over the real > issue. Adding "linux-arch" mailing list to ask architecture > maintainers to check their implementation of the atomic ops that > return a truth value.
For example, looking at the x86-32 version, I see this:
static inline int atomic64_add_unless(atomic64_t *v, long long a, long long u) ... return (int)a;
which looks really horribly wrong, but the assembly implementation actually returns 0/1 in %eax so it ends up being right - just confusingly so.
Also, to make things more confusing, the underscore version (__atomic_add_unless()) actually returns the old value, not the truth value of the comparison.
So this area definitely is messy. The x86-64 versions actually look fairly clean and return nice boolean values.
Linus
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