Re: [PATCH] qspinlock: use signed temporaries for cmpxchg

[Peter Zijlstra]

On Mon, Oct 26, 2020 at 05:57:51PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
> 
> When building with W=2, the build log is flooded with
> 
> include/asm-generic/qrwlock.h:65:56: warning: pointer targets in passing argument 2 of 'atomic_try_cmpxchg_acquire' differ in signedness [-Wpointer-sign]
> include/asm-generic/qrwlock.h:92:53: warning: pointer targets in passing argument 2 of 'atomic_try_cmpxchg_acquire' differ in signedness [-Wpointer-sign]
> include/asm-generic/qspinlock.h:68:55: warning: pointer targets in passing argument 2 of 'atomic_try_cmpxchg_acquire' differ in signedness [-Wpointer-sign]
> include/asm-generic/qspinlock.h:82:52: warning: pointer targets in passing argument 2 of 'atomic_try_cmpxchg_acquire' differ in signedness [-Wpointer-sign]
> 
> The atomics are built on top of signed integers, but the caller
> doesn't actually care. Just use signed types as well.
> 

Yuck, no. This is actively wrong. All that code very much wants u32.