Messages in this thread | | | From | Marco Elver <> | Date | Thu, 21 May 2020 15:39:38 +0200 | Subject | Re: [PATCH -tip v2 09/11] data_race: Avoid nested statement expression |
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On Thu, 21 May 2020 at 15:31, Will Deacon <will@kernel.org> 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.GA21166@zn.tnic > > Signed-off-by: Marco Elver <elver@google.com> > > --- > > 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
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