* [PATCH] percpu: add __percpu to SHIFT_PERCPU_PTR
@ 2019-10-15 10:26 Ben Dooks
2019-10-17 18:13 ` Dennis Zhou
0 siblings, 1 reply; 4+ messages in thread
From: Ben Dooks @ 2019-10-15 10:26 UTC (permalink / raw)
To: linux-kernel
Cc: Ben Dooks, Dennis Zhou, Tejun Heo, Christoph Lameter, linux-kernel
The SHIFT_PERCPU_PTR() returns a pointer used by a number
of functions that expect the pointer to be __percpu annotated
(sparse address space 3). Adding __percpu to this makes the
following sparse warnings go away.
Note, this then creates the problem the __percup is marked
as noderef, which may need removing for some of the internal
functions, or to remove other warnings.
mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:385:13: got signed char *
mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:385:13: got signed char *
mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:385:13: got signed char *
mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:385:13: got signed char *
mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:401:13: got signed char *
mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:401:13: got signed char *
mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:401:13: got signed char *
mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:401:13: got signed char *
mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:429:13: got signed char *
mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:429:13: got signed char *
mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:429:13: got signed char *
mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:429:13: got signed char *
mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:445:13: got signed char *
mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:445:13: got signed char *
mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:445:13: got signed char *
mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
mm/vmstat.c:445:13: got signed char *
mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:763:29: got signed char *
mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:763:29: got signed char *
mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:763:29: got signed char *
mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:763:29: got signed char *
mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:825:29: got signed char *
mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:825:29: got signed char *
mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:825:29: got signed char *
mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
mm/vmstat.c:825:29: got signed char *
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
---
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: linux-kernel@vger.kernel.org
---
include/linux/percpu-defs.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
index a6fabd865211..a49b6c702598 100644
--- a/include/linux/percpu-defs.h
+++ b/include/linux/percpu-defs.h
@@ -229,7 +229,7 @@ do { \
* pointer value. The weird cast keeps both GCC and sparse happy.
*/
#define SHIFT_PERCPU_PTR(__p, __offset) \
- RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset))
+ RELOC_HIDE((typeof(*(__p)) __kernel __percpu __force *)(__p), (__offset))
#define per_cpu_ptr(ptr, cpu) \
({ \
--
2.23.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] percpu: add __percpu to SHIFT_PERCPU_PTR
2019-10-15 10:26 [PATCH] percpu: add __percpu to SHIFT_PERCPU_PTR Ben Dooks
@ 2019-10-17 18:13 ` Dennis Zhou
2019-11-25 22:41 ` Dennis Zhou
0 siblings, 1 reply; 4+ messages in thread
From: Dennis Zhou @ 2019-10-17 18:13 UTC (permalink / raw)
To: Ben Dooks
Cc: linux-kernel, Dennis Zhou, Tejun Heo, Christoph Lameter, linux-kernel
On Tue, Oct 15, 2019 at 11:26:15AM +0100, Ben Dooks wrote:
> The SHIFT_PERCPU_PTR() returns a pointer used by a number
> of functions that expect the pointer to be __percpu annotated
> (sparse address space 3). Adding __percpu to this makes the
> following sparse warnings go away.
>
> Note, this then creates the problem the __percup is marked
> as noderef, which may need removing for some of the internal
> functions, or to remove other warnings.
>
> mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:385:13: got signed char *
> mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:385:13: got signed char *
> mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:385:13: got signed char *
> mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:385:13: got signed char *
> mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:401:13: got signed char *
> mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:401:13: got signed char *
> mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:401:13: got signed char *
> mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:401:13: got signed char *
> mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:429:13: got signed char *
> mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:429:13: got signed char *
> mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:429:13: got signed char *
> mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:429:13: got signed char *
> mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:445:13: got signed char *
> mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:445:13: got signed char *
> mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:445:13: got signed char *
> mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
> mm/vmstat.c:445:13: got signed char *
> mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
> mm/vmstat.c:763:29: got signed char *
> mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
> mm/vmstat.c:763:29: got signed char *
> mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
> mm/vmstat.c:763:29: got signed char *
> mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
> mm/vmstat.c:763:29: got signed char *
> mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
> mm/vmstat.c:825:29: got signed char *
> mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
> mm/vmstat.c:825:29: got signed char *
> mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
> mm/vmstat.c:825:29: got signed char *
> mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
> mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
> mm/vmstat.c:825:29: got signed char *
>
> Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
> ---
> Cc: Dennis Zhou <dennis@kernel.org>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: linux-kernel@vger.kernel.org
> ---
> include/linux/percpu-defs.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
> index a6fabd865211..a49b6c702598 100644
> --- a/include/linux/percpu-defs.h
> +++ b/include/linux/percpu-defs.h
> @@ -229,7 +229,7 @@ do { \
> * pointer value. The weird cast keeps both GCC and sparse happy.
> */
> #define SHIFT_PERCPU_PTR(__p, __offset) \
> - RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset))
> + RELOC_HIDE((typeof(*(__p)) __kernel __percpu __force *)(__p), (__offset))
>
> #define per_cpu_ptr(ptr, cpu) \
> ({ \
> --
> 2.23.0
>
Hello,
I've applied it for-5.5.
Thanks,
Dennis
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] percpu: add __percpu to SHIFT_PERCPU_PTR
2019-10-17 18:13 ` Dennis Zhou
@ 2019-11-25 22:41 ` Dennis Zhou
2019-11-26 16:37 ` Luc Van Oostenryck
0 siblings, 1 reply; 4+ messages in thread
From: Dennis Zhou @ 2019-11-25 22:41 UTC (permalink / raw)
To: Dennis Zhou
Cc: Ben Dooks, linux-kernel, Tejun Heo, Christoph Lameter, linux-kernel
On Thu, Oct 17, 2019 at 02:13:01PM -0400, Dennis Zhou wrote:
> On Tue, Oct 15, 2019 at 11:26:15AM +0100, Ben Dooks wrote:
> > The SHIFT_PERCPU_PTR() returns a pointer used by a number
> > of functions that expect the pointer to be __percpu annotated
> > (sparse address space 3). Adding __percpu to this makes the
> > following sparse warnings go away.
> >
> > Note, this then creates the problem the __percup is marked
> > as noderef, which may need removing for some of the internal
> > functions, or to remove other warnings.
> >
> > mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:385:13: got signed char *
> > mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:385:13: got signed char *
> > mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:385:13: got signed char *
> > mm/vmstat.c:385:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:385:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:385:13: got signed char *
> > mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:401:13: got signed char *
> > mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:401:13: got signed char *
> > mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:401:13: got signed char *
> > mm/vmstat.c:401:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:401:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:401:13: got signed char *
> > mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:429:13: got signed char *
> > mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:429:13: got signed char *
> > mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:429:13: got signed char *
> > mm/vmstat.c:429:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:429:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:429:13: got signed char *
> > mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:445:13: got signed char *
> > mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:445:13: got signed char *
> > mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:445:13: got signed char *
> > mm/vmstat.c:445:13: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:445:13: expected signed char [noderef] [usertype] <asn:3> *__p
> > mm/vmstat.c:445:13: got signed char *
> > mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
> > mm/vmstat.c:763:29: got signed char *
> > mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
> > mm/vmstat.c:763:29: got signed char *
> > mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
> > mm/vmstat.c:763:29: got signed char *
> > mm/vmstat.c:763:29: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:763:29: expected signed char [noderef] <asn:3> *__p
> > mm/vmstat.c:763:29: got signed char *
> > mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
> > mm/vmstat.c:825:29: got signed char *
> > mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
> > mm/vmstat.c:825:29: got signed char *
> > mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
> > mm/vmstat.c:825:29: got signed char *
> > mm/vmstat.c:825:29: warning: incorrect type in initializer (different address spaces)
> > mm/vmstat.c:825:29: expected signed char [noderef] <asn:3> *__p
> > mm/vmstat.c:825:29: got signed char *
> >
> > Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
> > ---
> > Cc: Dennis Zhou <dennis@kernel.org>
> > Cc: Tejun Heo <tj@kernel.org>
> > Cc: Christoph Lameter <cl@linux.com>
> > Cc: linux-kernel@vger.kernel.org
> > ---
> > include/linux/percpu-defs.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
> > index a6fabd865211..a49b6c702598 100644
> > --- a/include/linux/percpu-defs.h
> > +++ b/include/linux/percpu-defs.h
> > @@ -229,7 +229,7 @@ do { \
> > * pointer value. The weird cast keeps both GCC and sparse happy.
> > */
> > #define SHIFT_PERCPU_PTR(__p, __offset) \
> > - RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset))
> > + RELOC_HIDE((typeof(*(__p)) __kernel __percpu __force *)(__p), (__offset))
> >
> > #define per_cpu_ptr(ptr, cpu) \
> > ({ \
> > --
> > 2.23.0
> >
>
> Hello,
>
> I've applied it for-5.5.
>
> Thanks,
> Dennis
Hi Ben,
I've reverted this commit. After spending a little more time on it, I
don't think this is the fix we want because after we call RELOC_HIDE,
we are shifting from __percpu to __kernel address spaces as we're adding
the offset here.
Thanks,
Dennis
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] percpu: add __percpu to SHIFT_PERCPU_PTR
2019-11-25 22:41 ` Dennis Zhou
@ 2019-11-26 16:37 ` Luc Van Oostenryck
0 siblings, 0 replies; 4+ messages in thread
From: Luc Van Oostenryck @ 2019-11-26 16:37 UTC (permalink / raw)
To: Dennis Zhou
Cc: Ben Dooks, linux-kernel, Tejun Heo, Christoph Lameter, linux-kernel
On Mon, Nov 25, 2019 at 05:41:19PM -0500, Dennis Zhou wrote:
> On Thu, Oct 17, 2019 at 02:13:01PM -0400, Dennis Zhou wrote:
> > On Tue, Oct 15, 2019 at 11:26:15AM +0100, Ben Dooks wrote:
> > > The SHIFT_PERCPU_PTR() returns a pointer used by a number
> > > of functions that expect the pointer to be __percpu annotated
> > > (sparse address space 3). Adding __percpu to this makes the
> > > following sparse warnings go away.
> > >
> > > Note, this then creates the problem the __percup is marked
> > > as noderef, which may need removing for some of the internal
> > > functions, or to remove other warnings.
> > >
> > > diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
> > > index a6fabd865211..a49b6c702598 100644
> > > --- a/include/linux/percpu-defs.h
> > > +++ b/include/linux/percpu-defs.h
> > > @@ -229,7 +229,7 @@ do { \
> > > * pointer value. The weird cast keeps both GCC and sparse happy.
> > > */
> > > #define SHIFT_PERCPU_PTR(__p, __offset) \
> > > - RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset))
> > > + RELOC_HIDE((typeof(*(__p)) __kernel __percpu __force *)(__p), (__offset))
> > >
> > > #define per_cpu_ptr(ptr, cpu) \
> > > ({ \
> > > --
> > > 2.23.0
> > >
>
> Hi Ben,
>
> I've reverted this commit. After spending a little more time on it, I
> don't think this is the fix we want because after we call RELOC_HIDE,
> we are shifting from __percpu to __kernel address spaces as we're adding
> the offset here.
I agree. SHIFT_PERCPU_PTR()'s type is as designed.
Also, it should be noted that this warning doesn't exist on x86.
The problem lies in include/asm-generic/percpu.h, in this case within:
#define raw_cpu_generic_add_return(pcp, val) \
({ \
typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
\
*__p += val; \
*__p; \
})
There, the variable __p is declared as a __percpu pointer but:
1) the value assigned to it, the return value of raw_cpu_ptr(), is not
a plain (__kernel) pointer.
2) the variable is dereferenced just after when a __percpu pointer
is implicitly __noderef.
It's thus not SHIFT_PERCPU_PTR() or raw_cpu_ptr() that must have
their return type changed but the declaration of __p.
Here is a quick patch, only compile & sparse tested on mm/vmstat.c:
diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
index c2de013b2..757b667ca 100644
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -74,7 +74,7 @@ do { \
#define raw_cpu_generic_add_return(pcp, val) \
({ \
- typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
+ typeof(pcp) __kernel __force *__p = raw_cpu_ptr(&(pcp)); \
\
*__p += val; \
*__p; \
Note: the same problem is present in raw_cpu_generic_xchg(),
raw_cpu_generic_cmpxchg() & raw_cpu_generic_cmpxchg_double()
I need more testing and to evaluate possible side-effects before
sending a proper patch.
Best regards,
-- Luc Van Oostenryck
^ permalink raw reply related [flat|nested] 4+ messages in thread
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2019-10-15 10:26 [PATCH] percpu: add __percpu to SHIFT_PERCPU_PTR Ben Dooks
2019-10-17 18:13 ` Dennis Zhou
2019-11-25 22:41 ` Dennis Zhou
2019-11-26 16:37 ` Luc Van Oostenryck
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