tsan: update docs
update docs for no_sanitize_thread attribute and blacklist
llvm-svn: 192872
diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst
index 87558f0..cd526c7 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -1937,8 +1937,8 @@
Use ``__attribute__((no_sanitize_thread))`` on a function declaration
to specify that checks for data races on plain (non-atomic) memory accesses
should not be inserted by ThreadSanitizer.
-The function may still be instrumented by the tool
-to avoid false positives in other places.
+The function is still instrumented by the tool to avoid false positives and
+provide meaningful stack traces.
.. _langext-memory_sanitizer:
diff --git a/clang/docs/ThreadSanitizer.rst b/clang/docs/ThreadSanitizer.rst
index f543333..194ad4a 100644
--- a/clang/docs/ThreadSanitizer.rst
+++ b/clang/docs/ThreadSanitizer.rst
@@ -91,7 +91,8 @@
One may use the function attribute
:ref:`no_sanitize_thread <langext-thread_sanitizer>`
to disable instrumentation of plain (non-atomic) loads/stores in a particular function.
-ThreadSanitizer may still instrument such functions to avoid false positives.
+ThreadSanitizer still instruments such functions to avoid false positives and
+provide meaningful stack traces.
This attribute may not be
supported by other compilers, so we suggest to use it together with
``__has_feature(thread_sanitizer)``.
@@ -101,7 +102,10 @@
ThreadSanitizer supports ``src`` and ``fun`` entity types in
:doc:`SanitizerSpecialCaseList`, that can be used to suppress data race reports in
-the specified source files or functions.
+the specified source files or functions. Unlike functions marked with
+:ref:`no_sanitize_thread <langext-thread_sanitizer>` attribute,
+blacklisted functions are not instrumented at all. This can lead to false positives
+due to missed synchronization via atomic operations and missed stack frames in reports.
Limitations
-----------