On 2019-10-16, Tejun Heo <tj@xxxxxxxxxx> wrote: > Hello, Aleksa. > > On Wed, Oct 16, 2019 at 07:32:19PM +1100, Aleksa Sarai wrote: > > Maybe I'm misunderstanding Documentation/atomic_t.txt, but it looks to > > me like it's explicitly saying that I shouldn't use atomic64_t if I'm > > just using it for fetching and assignment. > > Hah, where is it saying that? Isn't that what this says: > Therefore, if you find yourself only using the Non-RMW operations of > atomic_t, you do not in fact need atomic_t at all and are doing it > wrong. Doesn't using just atomic64_read() and atomic64_set() fall under "only using the non-RMW operations of atomic_t"? But yes, I agree that any locking is overkill. > > As for 64-bit on 32-bit machines -- that is a separate issue, but from > > [1] it seems to me like there are more problems that *_ONCE() fixes than > > just split reads and writes. > > Your explanations are too wishy washy. If you wanna fix it, please do > it correctly. R/W ONCE isn't the right solution here. Sure, I will switch it to use atomic64_read() and atomic64_set() instead if that's what you'd prefer. Though I will mention that on quite a few architectures atomic64_read() is defined as: #define atomic64_read(v) READ_ONCE((v)->counter) -- Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH <https://www.cyphar.com/>
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