From: Marco Elver <elver@google.com>
To: elver@google.com
Cc: paulmck@kernel.org, dvyukov@google.com, glider@google.com,
andreyknvl@google.com, cai@lca.pw, kasan-dev@googlegroups.com,
linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>
Subject: [PATCH 2/2] kcsan: Change data_race() to no longer require marking racing accesses
Date: Tue, 31 Mar 2020 21:32:33 +0200 [thread overview]
Message-ID: <20200331193233.15180-2-elver@google.com> (raw)
In-Reply-To: <20200331193233.15180-1-elver@google.com>
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.
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
--
2.26.0.rc2.310.g2932bb562d-goog
next prev parent reply other threads:[~2020-03-31 19:33 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-31 19:32 [PATCH 1/2] kcsan: Move kcsan_{disable,enable}_current() to kcsan-checks.h Marco Elver
2020-03-31 19:32 ` Marco Elver [this message]
2020-04-01 8:38 ` [PATCH 2/2] kcsan: Change data_race() to no longer require marking racing accesses Will Deacon
2020-03-31 22:55 ` [PATCH 1/2] kcsan: Move kcsan_{disable,enable}_current() to kcsan-checks.h Paul E. McKenney
2020-04-01 8:40 ` Will Deacon
2020-04-01 16:37 ` Paul E. McKenney
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