[PATCH 5/6] sh: Emulate two-byte cmpxchg

[Paul E. McKenney]

On Wed, Sep 16, 2026 at 09:16:16PM +0200, John Paul Adrian Glaubitz wrote:
> Hi Bradley,
> 
> On Fri, 2026-09-11 at 19:25 +0000, Bradley Morgan wrote:
> > SH has no byte or halfword atomic memory operations, so the
> > __cmpxchg() switch routes case 1 through cmpxchg_emu_u8() and
> > lets case 2 fall through to __cmpxchg_called_with_bad_pointer(),
> > which is declared but never defined, so a two-byte cmpxchg()
> > fails at link time. Route case 2 through the new cmpxchg_emu_u16().
> > 
> > Signed-off-by: Bradley Morgan <brads at mainlining.org>
> > ---
> >  arch/sh/include/asm/cmpxchg.h | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/arch/sh/include/asm/cmpxchg.h b/arch/sh/include/asm/cmpxchg.h
> > index 1e5dc5ccf7bf..477d3025a441 100644
> > --- a/arch/sh/include/asm/cmpxchg.h
> > +++ b/arch/sh/include/asm/cmpxchg.h
> > @@ -59,6 +59,8 @@ static inline unsigned long __cmpxchg(volatile void * ptr, unsigned long old,
> >  	switch (size) {
> >  	case 1:
> >  		return cmpxchg_emu_u8(ptr, old, new);
> > +	case 2:
> > +		return cmpxchg_emu_u16(ptr, old, new);
> >  	case 4:
> >  		return __cmpxchg_u32(ptr, old, new);
> >  	}
> 
> Odd, I thought this series was merged long time ago. Was there anything holding it back?

You might be thinking of the cmpxchg_emu_u8() series from a few years back.
This is cmpxchg_emu_u16().

							Thanx, Paul

> Either way:
> 
> Acked-by: John Paul Adrian Glaubitz <glaubitz at physik.fu-berlin.de>
> 
> Adrian
> 
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