[PATCH v2 15/23] locking/barriers, kcsan: Support generic instrumentation

From: Marco Elver
Date: Thu Nov 18 2021 - 03:14:18 EST

Thus far only smp_*() barriers had been defined by asm-generic/barrier.h
based on __smp_*() barriers, because the !SMP case is usually generic.

With the introduction of instrumentation, it also makes sense to have
asm-generic/barrier.h assist in the definition of instrumented versions
of mb(), rmb(), wmb(), dma_rmb(), and dma_wmb().

Because there is no requirement to distinguish the !SMP case, the
definition can be simpler: we can avoid also providing fallbacks for the
__ prefixed cases, and only check if `defined(__<barrier>)`, to finally
define the KCSAN-instrumented versions.

This also allows for the compiler to complain if an architecture
accidentally defines both the normal and __ prefixed variant.

Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
include/asm-generic/barrier.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
index 27a9c9edfef6..02c4339c8eeb 100644
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -21,6 +21,31 @@
#define nop() asm volatile ("nop")

+ * Architectures that want generic instrumentation can define __ prefixed
+ * variants of all barriers.
+ */
+#ifdef __mb
+#define mb() do { kcsan_mb(); __mb(); } while (0)
+#ifdef __rmb
+#define rmb() do { kcsan_rmb(); __rmb(); } while (0)
+#ifdef __wmb
+#define wmb() do { kcsan_wmb(); __wmb(); } while (0)
+#ifdef __dma_rmb
+#define dma_rmb() do { kcsan_rmb(); __dma_rmb(); } while (0)
+#ifdef __dma_wmb
+#define dma_wmb() do { kcsan_wmb(); __dma_wmb(); } while (0)
* Force strict CPU ordering. And yes, this is required on UP too when we're
* talking to devices.