[PATCH 2/3] kcsan: Clarify Kconfig option KCSAN_IGNORE_ATOMICS

[Marco Elver <elver@google.com>]

Clarify difference between options KCSAN_IGNORE_ATOMICS and
KCSAN_ASSUME_PLAIN_WRITES_ATOMIC in help text.

Signed-off-by: Marco Elver <elver@google.com>
---
 lib/Kconfig.kcsan | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index 08972376f0454..35fab63111d75 100644
--- a/lib/Kconfig.kcsan
+++ b/lib/Kconfig.kcsan
@@ -131,8 +131,17 @@ config KCSAN_ASSUME_PLAIN_WRITES_ATOMIC
 config KCSAN_IGNORE_ATOMICS
 	bool "Do not instrument marked atomic accesses"
 	help
-	  If enabled, never instruments marked atomic accesses. This results in
-	  not reporting data races where one access is atomic and the other is
-	  a plain access.
+	  Never instrument marked atomic accesses. This option can be used for
+	  more advanced filtering. Conflicting marked atomic reads and plain
+	  writes will never be reported as a data race, however, will cause
+	  plain reads and marked writes to result in "unknown origin" reports.
+	  If combined with CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN=n, data
+	  races where at least one access is marked atomic will never be
+	  reported.
+
+	  Like KCSAN_ASSUME_PLAIN_WRITES_ATOMIC, conflicting marked atomic
+	  reads and plain writes will not be reported as data races, however,
+	  unlike that option, data races due to two conflicting plain writes
+	  will be reported (if CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=n).
 
 endif # KCSAN
-- 
2.25.0.341.g760bfbb309-goog