path: root/scripts/Makefile.kcsan
diff options
authorMarco Elver <>2020-07-24 09:00:01 +0200
committerPaul E. McKenney <>2020-08-24 15:09:32 -0700
commit14e2ac8de0f91f12122a49f09897b0cd05256460 (patch)
tree938e24729e65eb3eed3403e7f084fbcfa8dbbcdc /scripts/Makefile.kcsan
parentf9ea63193135473ed6b6ff06f016eb6248100041 (diff)
kcsan: Support compounded read-write instrumentation
Add support for compounded read-write instrumentation if supported by the compiler. Adds the necessary instrumentation functions, and a new type which is used to generate a more descriptive report. Furthermore, such compounded memory access instrumentation is excluded from the "assume aligned writes up to word size are atomic" rule, because we cannot assume that the compiler emits code that is atomic for compound ops. LLVM/Clang added support for the feature in: The new instrumentation is emitted for sets of memory accesses in the same basic block to the same address with at least one read appearing before a write. These typically result from compound operations such as ++, --, +=, -=, |=, &=, etc. but also equivalent forms such as "var = var + 1". Where the compiler determines that it is equivalent to emit a call to a single __tsan_read_write instead of separate __tsan_read and __tsan_write, we can then benefit from improved performance and better reporting for such access patterns. The new reports now show that the ops are both reads and writes, for example: read-write to 0xffffffff90548a38 of 8 bytes by task 143 on cpu 3: test_kernel_rmw_array+0x45/0xa0 access_thread+0x71/0xb0 kthread+0x21e/0x240 ret_from_fork+0x22/0x30 read-write to 0xffffffff90548a38 of 8 bytes by task 144 on cpu 2: test_kernel_rmw_array+0x45/0xa0 access_thread+0x71/0xb0 kthread+0x21e/0x240 ret_from_fork+0x22/0x30 Acked-by: Peter Zijlstra (Intel) <> Signed-off-by: Marco Elver <> Signed-off-by: Paul E. McKenney <>
Diffstat (limited to 'scripts/Makefile.kcsan')
1 files changed, 1 insertions, 1 deletions
diff --git a/scripts/Makefile.kcsan b/scripts/Makefile.kcsan
index c50f27b3ac56..c37f9518d5d9 100644
--- a/scripts/Makefile.kcsan
+++ b/scripts/Makefile.kcsan
@@ -11,5 +11,5 @@ endif
# of some options does not break KCSAN nor causes false positive reports.
CFLAGS_KCSAN := -fsanitize=thread \
$(call cc-option,$(call cc-param,tsan-instrument-func-entry-exit=0) -fno-optimize-sibling-calls) \
- $(call cc-option,$(call cc-param,tsan-instrument-read-before-write=1)) \
+ $(call cc-option,$(call cc-param,tsan-compound-read-before-write=1),$(call cc-option,$(call cc-param,tsan-instrument-read-before-write=1))) \
$(call cc-param,tsan-distinguish-volatile=1)