Messages in this thread | | | Date | Wed, 1 Apr 2020 09:38:19 +0100 | From | Will Deacon <> | Subject | Re: [PATCH 2/2] kcsan: Change data_race() to no longer require marking racing accesses |
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On Tue, Mar 31, 2020 at 09:32:33PM +0200, Marco Elver wrote: > Thus far, accesses marked with data_race() would still require the > racing access to be marked in some way (be it with READ_ONCE(), > WRITE_ONCE(), or data_race() itself), as otherwise KCSAN would still > report a data race. This requirement, however, seems to be unintuitive, > and some valid use-cases demand *not* marking other accesses, as it > might hide more serious bugs (e.g. diagnostic reads). > > Therefore, this commit changes data_race() to no longer require marking > racing accesses (although it's still recommended if possible). > > The alternative would have been introducing another variant of > data_race(), however, since usage of data_race() already needs to be > carefully reasoned about, distinguishing between these cases likely adds > more complexity in the wrong place.
Just a thought, but perhaps worth extending scripts/checkpatch.pl to check for use of data_race() without a comment? We already have that for memory barriers, so should be easy enough to extend with any luck.
> Link: https://lkml.kernel.org/r/20200331131002.GA30975@willie-the-truck > Signed-off-by: Marco Elver <elver@google.com> > Cc: Paul E. McKenney <paulmck@kernel.org> > Cc: Will Deacon <will@kernel.org> > Cc: Qian Cai <cai@lca.pw> > --- > include/linux/compiler.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index f504edebd5d7..1729bd17e9b7 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -326,9 +326,9 @@ unsigned long read_word_at_a_time(const void *addr) > #define data_race(expr) \ > ({ \ > typeof(({ expr; })) __val; \ > - kcsan_nestable_atomic_begin(); \ > + kcsan_disable_current(); \ > __val = ({ expr; }); \ > - kcsan_nestable_atomic_end(); \ > + kcsan_enable_current(); \ > __val; \ > }) > #else
Acked-by: Will Deacon <will@kernel.org>
Will
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