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Date:   Tue,  4 Feb 2020 18:21:11 +0100
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Subject: [PATCH v2 2/3] kcsan: Clarify Kconfig option KCSAN_IGNORE_ATOMICS
From:   Marco Elver <elver@google.com>
To:     elver@google.com
Cc:     paulmck@kernel.org, andreyknvl@google.com, glider@google.com,
        dvyukov@google.com, kasan-dev@googlegroups.com,
        linux-kernel@vger.kernel.org
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Clarify difference between options KCSAN_IGNORE_ATOMICS and
KCSAN_ASSUME_PLAIN_WRITES_ATOMIC in help text.

Signed-off-by: Marco Elver <elver@google.com>
---
v2:
* Update help text to mention alignment w.r.t. previous option.
---
 lib/Kconfig.kcsan | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index 66126853dab02..020ac63e43617 100644
--- a/lib/Kconfig.kcsan
+++ b/lib/Kconfig.kcsan
@@ -132,8 +132,18 @@ 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
+	  additional 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.
+
+	  Similar to KCSAN_ASSUME_PLAIN_WRITES_ATOMIC, but including unaligned
+	  accesses, 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 (aligned and
+	  unaligned, if CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=n).
 
 endif # KCSAN
-- 
2.25.0.341.g760bfbb309-goog