linux-kernel - Re: arch/arc/kernel/smp.c:267:18: sparse: sparse: cast removes address space '_

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Message-ID: <5ada7b12-f3c4-4ae8-b396-a3e474f4f852@paulmck-laptop>
Date: Fri, 4 Oct 2024 08:41:26 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: kernel test robot <lkp@...el.com>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
	linux-snps-arc@...ts.infradead.org
Subject: Re: arch/arc/kernel/smp.c:267:18: sparse: sparse: cast removes
 address space '__percpu' of expression

On Mon, Sep 30, 2024 at 09:10:27AM -0700, Paul E. McKenney wrote:
> On Wed, Sep 25, 2024 at 01:40:45PM +0800, kernel test robot wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head:   684a64bf32b6e488004e0ad7f0d7e922798f65b6
> > commit: f2519d4d4fc4d36f2b58c5614357de9f5b4032fc ARC: Emulate one-byte cmpxchg
> > date:   12 days ago
> > config: arc-randconfig-r123-20240925 (https://download.01.org/0day-ci/archive/20240925/202409251336.ToC0TvWB-lkp@intel.com/config)
> > compiler: arc-elf-gcc (GCC) 13.2.0
> > reproduce: (https://download.01.org/0day-ci/archive/20240925/202409251336.ToC0TvWB-lkp@intel.com/reproduce)
> > 
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@...el.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202409251336.ToC0TvWB-lkp@intel.com/
> > 
> > sparse warnings: (new ones prefixed by >>)
> >    arch/arc/kernel/smp.c:252:48: sparse: sparse: incorrect type in initializer (different address spaces) @@     expected unsigned long [noderef] __percpu *ipi_data_ptr @@     got unsigned long * @@
> >    arch/arc/kernel/smp.c:252:48: sparse:     expected unsigned long [noderef] __percpu *ipi_data_ptr
> >    arch/arc/kernel/smp.c:252:48: sparse:     got unsigned long *
> >    arch/arc/kernel/smp.c:267:18: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected void const volatile *v @@     got unsigned long [noderef] __percpu *__ai_ptr @@
> >    arch/arc/kernel/smp.c:267:18: sparse:     expected void const volatile *v
> >    arch/arc/kernel/smp.c:267:18: sparse:     got unsigned long [noderef] __percpu *__ai_ptr
> > >> arch/arc/kernel/smp.c:267:18: sparse: sparse: cast removes address space '__percpu' of expression
> > >> arch/arc/kernel/smp.c:267:18: sparse: sparse: cast removes address space '__percpu' of expression
> 
> I could "fix" this using __force.  Is that a reasonable approach?
> 
> If I don't hear otherwise, I will take that approach.

Having not heard otherwise, does the following fix this issue for you?

							Thanx, Paul

------------------------------------------------------------------------

diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
index 58045c8983404..76f43db0890fc 100644
--- a/arch/arc/include/asm/cmpxchg.h
+++ b/arch/arc/include/asm/cmpxchg.h
@@ -48,7 +48,7 @@
 									\
 	switch(sizeof((_p_))) {						\
 	case 1:								\
-		_prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_);	\
+		_prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *__force)_p_, (uintptr_t)_o_, (uintptr_t)_n_);	\
 		break;							\
 	case 4:								\
 		_prev_ = __cmpxchg(_p_, _o_, _n_);			\