Re: [PATCH] riscv/atomic: Do proper sign extension also for unsigned in arch_cmpxchg

[Andreas Schwab]

On Jan 30 2025, Alexandre Ghiti wrote:

> That's a nice catch indeed. IIUC, we have the same issue here
> https://elixir.bootlin.com/linux/v6.13/source/arch/riscv/include/asm/futex.h#L89
> right?

Indeed, though it doesn't result in wrong code currently.  This is
because the compare value is passed unmodified as u32 to the asm and the
compiler keeps the value sign extended in registers.  That would break
if you would add a cast to long like in commit 6c58f25e6938 as that
would erroneously zero extend it.

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Andreas Schwab, SUSE Labs, schwab@xxxxxxx
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