Messages in this thread | | | Date | Fri, 4 Feb 2022 11:16:02 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH v2] atomics: fix atomic64_{read_acquire,set_release} fallbacks |
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On Fri, Feb 04, 2022 at 08:20:25AM +0800, Boqun Feng wrote: > On Thu, Feb 03, 2022 at 04:12:43PM +0000, Mark Rutland wrote: > > diff --git a/include/linux/atomic/atomic-arch-fallback.h b/include/linux/atomic/atomic-arch-fallback.h > > index a3dba31df01e..6db58d180866 100644 > > --- a/include/linux/atomic/atomic-arch-fallback.h > > +++ b/include/linux/atomic/atomic-arch-fallback.h > > @@ -151,7 +151,16 @@ > > static __always_inline int > > arch_atomic_read_acquire(const atomic_t *v) > > { > > - return smp_load_acquire(&(v)->counter); > > + int ret; > > + > > + if (__native_word(atomic_t)) { > > + ret = smp_load_acquire(&(v)->counter); > > + } else { > > + ret = arch_atomic_read(v); > > + __atomic_acquire_fence(); > > + } > > + > > + return ret; > > } > > #define arch_atomic_read_acquire arch_atomic_read_acquire > > #endif > > @@ -160,7 +169,12 @@ arch_atomic_read_acquire(const atomic_t *v) > > static __always_inline void > > arch_atomic_set_release(atomic_t *v, int i) > > { > > - smp_store_release(&(v)->counter, i); > > + if (__native_word(atomic_t)) { > > + smp_store_release(&(v)->counter, i); > > + } else { > > + __atomic_release_fence(); > > + arch_atomic_set(v, i); > > + } > > } > > The changes for atomic_t are not necessary, right? They are correct but > "side effects" because of the change in scripts.
Correct -- those aren't necessary, but aren't harmful, and it's simpler to have than than it is to special-case the scripts.
> If so, it's better to mention this somewhere.
Sure; how about I add the following to the commit message:
| Since the fallback templates are used to generate the atomic64_*() and | atomic_*() operations, the __native_word() check is added to both. For | the atomic_*() operations, which are always 32-bit, the __native_word() | check is redundant but not harmful, as it is always true.
... ?
Thanks, Mark.
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