Subject: linux-next: build warning after merge of the net-next tree

From: Stephen Rothwell <[email-masked]>
Date: Mon, 11 Nov 2019 12:39:22 +1100

Hi all,

After merging the net-next tree, today's linux-next build (powerpc
ppc64_defconfig) produced this warning:

In file included from ./arch/powerpc/include/generated/asm/local64.h:1,
                 from include/linux/u64_stats_sync.h:72,
                 from include/linux/cgroup-defs.h:20,
                 from include/linux/cgroup.h:28,
                 from include/linux/memcontrol.h:13,
                 from include/linux/swap.h:9,
                 from include/linux/suspend.h:5,
                 from arch/powerpc/kernel/asm-offsets.c:23:
include/linux/u64_stats_sync.h: In function 'u64_stats_read':
include/asm-generic/local64.h:30:37: warning: passing argument 1 of 'local_read' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
   30 | #define local64_read(l)  local_read(&(l)->a)
      |                                     ^~~~~~~
include/linux/u64_stats_sync.h:80:9: note: in expansion of macro 'local64_read'
   80 |  return local64_read(&p->v);
      |         ^~~~~~~~~~~~
In file included from include/asm-generic/local64.h:22,
                 from ./arch/powerpc/include/generated/asm/local64.h:1,
                 from include/linux/u64_stats_sync.h:72,
                 from include/linux/cgroup-defs.h:20,
                 from include/linux/cgroup.h:28,
                 from include/linux/memcontrol.h:13,
                 from include/linux/swap.h:9,
                 from include/linux/suspend.h:5,
                 from arch/powerpc/kernel/asm-offsets.c:23:
arch/powerpc/include/asm/local.h:20:44: note: expected 'local_t *' {aka 'struct <anonymous> *'} but argument is of type 'const local_t *' {aka 'const struct <anonymous> *'}
   20 | static __inline__ long local_read(local_t *l)
      |                                   ~~~~~~~~~^

Introduced by commit

  316580b69d0a ("u64_stats: provide u64_stats_t type")

Powerpc folks: is there some reason that local_read() cannot take a
const argument?

I have added this patch (which builds fine) for today:

From: Stephen Rothwell <[email-masked]>
Date: Mon, 11 Nov 2019 12:32:24 +1100
Subject: [PATCH] powerpc: local_read() should take a const local_t argument

Signed-off-by: Stephen Rothwell <[email-masked]>
---
 arch/powerpc/include/asm/local.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/local.h b/arch/powerpc/include/asm/local.h
index fdd00939270b..bc4bd19b7fc2 100644
--- a/arch/powerpc/include/asm/local.h
+++ b/arch/powerpc/include/asm/local.h
@@ -17,7 +17,7 @@ typedef struct
 
 #define LOCAL_INIT(i)	{ (i) }
 
-static __inline__ long local_read(local_t *l)
+static __inline__ long local_read(const local_t *l)
 {
 	return READ_ONCE(l->v);
 }
-- 
2.23.0

-- 
Cheers,
Stephen Rothwell