Messages in this thread | | | Date | Mon, 1 Feb 2016 22:53:53 +0100 | Subject | Re: [PATCH] kref: prefer atomic_inc_not_zero to atomic_add_unless | From | "Jason A. Donenfeld" <> |
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This was positively reviewed but never picked up. Can someone queue this for rc3?
Thanks, Jason
On Sun, Oct 11, 2015 at 9:59 PM, Thomas Hellstrom <thellstrom@vmware.com> wrote: > Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com> > > > On 10/10/2015 12:56 PM, Jason A. Donenfeld wrote: >> On most platforms, there exists this ifdef: >> >> #define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0) >> >> This makes this patch functionally useless. However, on PPC, there is >> actually an explicit definition of atomic_inc_not_zero with its own >> assembly that is slightly more optimized than atomic_add_unless. So, >> this patch changes kref to use atomic_inc_not_zero instead, for PPC and >> any future platforms that might provide an explicit implementation. >> >> This also puts this usage of kref more in line with a verbatim reading >> of the examples in Paul McKenney's paper [1] in the section titled "2.4 >> Atomic Counting With Check and Release Memory Barrier", which uses >> atomic_inc_not_zero. >> >> [1] https://urldefense.proofpoint.com/v2/url?u=http-3A__open-2Dstd.org_jtc1_sc22_wg21_docs_papers_2007_n2167.pdf&d=BQIBAg&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=vpukPkBtpoNQp2IUKuFviOmPNYWVKmen3Jeeu55zmEA&m=z5Nd9sYiJMKiphNjyZp6XT5CbayXMBlcb903f260pDY&s=HEHX3CuXRs2GRRQWuC4Vef6iJMwdilKVRkiZgJpjEpA&e= >> >> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> >> --- >> include/linux/kref.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/include/linux/kref.h b/include/linux/kref.h >> index 484604d..83d1f94 100644 >> --- a/include/linux/kref.h >> +++ b/include/linux/kref.h >> @@ -166,6 +166,6 @@ static inline int kref_put_mutex(struct kref *kref, >> */ >> static inline int __must_check kref_get_unless_zero(struct kref *kref) >> { >> - return atomic_add_unless(&kref->refcount, 1, 0); >> + return atomic_inc_not_zero(&kref->refcount); >> } >> #endif /* _KREF_H_ */ >
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