The following commit has been merged into the locking/kcsan branch of tip:
Commit-ID: 88f1be32068d4323aa31236452352d6019a03ccc
Gitweb: https://git.kernel.org/tip/88f1be32068d4323aa31236452352d6019a03ccc
Author: Will Deacon <will@xxxxxxxxxx>
AuthorDate: Mon, 11 May 2020 21:41:48 +01:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Tue, 12 May 2020 11:04:17 +02:00
kcsan: Rework data_race() so that it can be used by READ_ONCE()
Rework the data_race() macro so that it:
- Accepts expressions which evaluate to a 'const' type
- Attempts to discard volatile qualifiers from scalar types, avoiding
pointless stack spills
- Uses __kcsan_{disable,enable}_current(), allowing its use from code
that is built independently from the kernel, such as the vDSO
This will allow for its use by {READ,WRITE}_ONCE() in a subsequent patch.
At the same time, fix-up some weird whitespace issues.
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200511204150.27858-17-will@xxxxxxxxxx
---
include/linux/compiler.h | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 548294e..cb2e3b3 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -314,14 +314,15 @@ unsigned long read_word_at_a_time(const void *addr)
* This macro *does not* affect normal code generation, but is a hint
* to tooling that data races here are to be ignored.
*/
-#define data_race(expr) \
- ({ \
- typeof(({ expr; })) __val; \
- kcsan_disable_current(); \
- __val = ({ expr; }); \
- kcsan_enable_current(); \
- __val; \
- })
+#define data_race(expr) \
+({ \
+ __kcsan_disable_current(); \
+ ({ \
+ __unqual_scalar_typeof(({ expr; })) __v = ({ expr; }); \
+ __kcsan_enable_current(); \
+ __v; \
+ }); \
+})
#endif /* __KERNEL__ */
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