Messages in this thread | | | Date | Fri, 27 Jan 2023 12:18:13 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] locking/atomic: atomic: Use arch_atomic_{read,set} in generic atomic ops |
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On Thu, Jan 26, 2023 at 06:33:54PM +0100, Jules Maselbas wrote:
> @@ -58,9 +61,11 @@ static inline int generic_atomic_fetch_##op(int i, atomic_t *v) \ > static inline void generic_atomic_##op(int i, atomic_t *v) \ > { \ > unsigned long flags; \ > + int c; \ > \ > raw_local_irq_save(flags); \ > - v->counter = v->counter c_op i; \ > + c = arch_atomic_read(v); \ > + arch_atomic_set(v, c c_op i); \ > raw_local_irq_restore(flags); \ > }
This and the others like it are a bit sad, it explicitly dis-allows the compiler from using memops and forces a load-store.
The alternative is writing it like:
*(volatile int *)&v->counter c_op i;
but that's pretty shit too I suppose.
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