The following commit has been merged into the locking/kcsan branch of tip:
Commit-ID: cdd28ad2d8110099e43527e96d059c5639809680
Gitweb:
https://git.kernel.org/tip/cdd28ad2d8110099e43527e96d059c5639809680
Author: Will Deacon <[email protected]>
AuthorDate: Mon, 11 May 2020 21:41:49 +01:00
Committer: Thomas Gleixner <[email protected]>
CommitterDate: Tue, 12 May 2020 11:04:17 +02:00
READ_ONCE: Use data_race() to avoid KCSAN instrumentation
Rather then open-code the disabling/enabling of KCSAN across the guts of
{READ,WRITE}_ONCE(), defer to the data_race() macro instead.
Signed-off-by: Will Deacon <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Marco Elver <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
include/linux/compiler.h | 54 +++++++++++++++++----------------------
1 file changed, 24 insertions(+), 30 deletions(-)
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index cb2e3b3..741c93c 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -199,6 +199,26 @@ void ftrace_likely_update(struct ftrace_likely_data *f,
int val,
#include <linux/kasan-checks.h>
#include <linux/kcsan-checks.h>
+/**
+ * data_race - mark an expression as containing intentional data races
+ *
+ * This data_race() macro is useful for situations in which data races
+ * should be forgiven. One example is diagnostic code that accesses
+ * shared variables but is not a part of the core synchronization design.
+ *
+ * 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)
\
+({ \
+ __kcsan_disable_current(); \
+ ({ \
+ __unqual_scalar_typeof(({ expr; })) __v = ({ expr; }); \
+ __kcsan_enable_current(); \
+ __v; \
+ }); \
+})
+
/*
* Use __READ_ONCE() instead of READ_ONCE() if you do not require any
* atomicity or dependency ordering guarantees. Note that this may result
@@ -209,14 +229,10 @@ void ftrace_likely_update(struct ftrace_likely_data *f,
int val,
#define __READ_ONCE_SCALAR(x) \
({ \
typeof(x) *__xp = &(x); \
+ __unqual_scalar_typeof(x) __x = data_race(__READ_ONCE(*__xp)); \
kcsan_check_atomic_read(__xp, sizeof(*__xp)); \
- __kcsan_disable_current(); \
- ({ \
- __unqual_scalar_typeof(x) __x = __READ_ONCE(*__xp); \
- __kcsan_enable_current(); \
- smp_read_barrier_depends(); \
- (typeof(x))__x; \
- }); \
+ smp_read_barrier_depends(); \
+ (typeof(x))__x; \
})
#define READ_ONCE(x) \
@@ -234,9 +250,7 @@ do {
\
do { \
typeof(x) *__xp = &(x); \
kcsan_check_atomic_write(__xp, sizeof(*__xp)); \
- __kcsan_disable_current(); \
- __WRITE_ONCE(*__xp, val); \
- __kcsan_enable_current(); \
+ data_race(({ __WRITE_ONCE(*__xp, val); 0; })); \
} while (0)
#define WRITE_ONCE(x, val) \
@@ -304,26 +318,6 @@ unsigned long read_word_at_a_time(const void *addr)
return *(unsigned long *)addr;
}
-/**
- * data_race - mark an expression as containing intentional data races
- *
- * This data_race() macro is useful for situations in which data races
- * should be forgiven. One example is diagnostic code that accesses
- * shared variables but is not a part of the core synchronization design.
- *
- * 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)
\
-({ \
- __kcsan_disable_current(); \
- ({ \
- __unqual_scalar_typeof(({ expr; })) __v = ({ expr; }); \
- __kcsan_enable_current(); \
- __v; \
- }); \
-})
-
#endif /* __KERNEL__ */
/*
