Re: [PATCH -tip v2 09/11] data_race: Avoid nested statement expression

2020-05-21 Thread Marco Elver 
On Thu, 21 May 2020 at 15:31, Will Deacon  wrote:
>
> On Thu, May 21, 2020 at 01:08:52PM +0200, Marco Elver wrote:
> > It appears that compilers have trouble with nested statements
> > expressions, as such make the data_race() macro be only a single
> > statement expression. This will help us avoid potential problems in
> > future as its usage increases.
> >
> > Link: https://lkml.kernel.org/r/20200520221712.ga21...@zn.tnic
> > Signed-off-by: Marco Elver 
> > ---
> > v2:
> > * Add patch to series in response to above linked discussion.
> > ---
> >  include/linux/compiler.h | 9 -
> >  1 file changed, 4 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> > index 7444f026eead..1f9bd9f35368 100644
> > --- a/include/linux/compiler.h
> > +++ b/include/linux/compiler.h
> > @@ -211,12 +211,11 @@ void ftrace_likely_update(struct ftrace_likely_data 
> > *f, int val,
> >   */
> >  #define data_race(expr)
> >   \
> >  ({   \
> > + __unqual_scalar_typeof(({ expr; })) __v;\
> >   __kcsan_disable_current();  \
> > - ({  \
> > - __unqual_scalar_typeof(({ expr; })) __v = ({ expr; });  \
> > - __kcsan_enable_current();   \
> > - __v;\
> > - }); \
> > + __v = ({ expr; });  \
> > + __kcsan_enable_current();   \
> > + __v;\
>
> Hopefully it doesn't matter, but this will run into issues with 'const'
> non-scalar expressions.

Good point. We could move the kcsan_disable_current() into ({
__kcsan_disable_current(); expr; }).

Will fix for v3.

Thanks,
-- Marco

> Will
>
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Re: [PATCH -tip v2 09/11] data_race: Avoid nested statement expression

2020-05-21 Thread Will Deacon 
On Thu, May 21, 2020 at 01:08:52PM +0200, Marco Elver wrote:
> It appears that compilers have trouble with nested statements
> expressions, as such make the data_race() macro be only a single
> statement expression. This will help us avoid potential problems in
> future as its usage increases.
> 
> Link: https://lkml.kernel.org/r/20200520221712.ga21...@zn.tnic
> Signed-off-by: Marco Elver 
> ---
> v2:
> * Add patch to series in response to above linked discussion.
> ---
>  include/linux/compiler.h | 9 -
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 7444f026eead..1f9bd9f35368 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -211,12 +211,11 @@ void ftrace_likely_update(struct ftrace_likely_data *f, 
> int val,
>   */
>  #define data_race(expr)  
> \
>  ({   \
> + __unqual_scalar_typeof(({ expr; })) __v;\
>   __kcsan_disable_current();  \
> - ({  \
> - __unqual_scalar_typeof(({ expr; })) __v = ({ expr; });  \
> - __kcsan_enable_current();   \
> - __v;\
> - }); \
> + __v = ({ expr; });  \
> + __kcsan_enable_current();   \
> + __v;\

Hopefully it doesn't matter, but this will run into issues with 'const'
non-scalar expressions.

Will

[PATCH -tip v2 09/11] data_race: Avoid nested statement expression

2020-05-21 Thread Marco Elver 
It appears that compilers have trouble with nested statements
expressions, as such make the data_race() macro be only a single
statement expression. This will help us avoid potential problems in
future as its usage increases.

Link: https://lkml.kernel.org/r/20200520221712.ga21...@zn.tnic
Signed-off-by: Marco Elver 
---
v2:
* Add patch to series in response to above linked discussion.
---
 include/linux/compiler.h | 9 -
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 7444f026eead..1f9bd9f35368 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -211,12 +211,11 @@ void ftrace_likely_update(struct ftrace_likely_data *f, 
int val,
  */
 #define data_race(expr)
\
 ({ \
+   __unqual_scalar_typeof(({ expr; })) __v;\
__kcsan_disable_current();  \
-   ({  \
-   __unqual_scalar_typeof(({ expr; })) __v = ({ expr; });  \
-   __kcsan_enable_current();   \
-   __v;\
-   }); \
+   __v = ({ expr; });  \
+   __kcsan_enable_current();   \
+   __v;\
 })
 
 /*
-- 
2.26.2.761.g0e0b3e54be-goog