[PATCH v2 4/4] docs/devel: update tsan build documentation

[Pierrick Bouvier]

Mention it's now possible to build with gcc, instead of clang, and
explain how to build a sanitized glib version.

Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
---
 docs/devel/testing.rst | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst
index af73d3d64fb..f10cfc3f786 100644
--- a/docs/devel/testing.rst
+++ b/docs/devel/testing.rst
@@ -634,20 +634,38 @@ Building and Testing with TSan
 It is possible to build and test with TSan, with a few additional steps.
 These steps are normally done automatically in the docker.
 
-There is a one time patch needed in clang-9 or clang-10 at this time:
+TSan is supported for clang and gcc.
+One particularity of sanitizers is that all the code, including shared objects
+dependencies, should be built with it.
+In the case of TSan, any synchronization primitive from glib (GMutex for
+instance) will not be recognized, and will lead to false positives.
+
+To build a tsan version of glib:
 
 .. code::
 
-  sed -i 's/^const/static const/g' \
-      /usr/lib/llvm-10/lib/clang/10.0.0/include/sanitizer/tsan_interface.h
+   $ git clone --depth=1 --branch=2.81.0 https://github.com/GNOME/glib.git
+   $ cd glib
+   $ CFLAGS="-O2 -g -fsanitize=thread" meson build
+   $ ninja -C build
 
 To configure the build for TSan:
 
 .. code::
 
-  ../configure --enable-tsan --cc=clang-10 --cxx=clang++-10 \
+  ../configure --enable-tsan \
                --disable-werror --extra-cflags="-O0"
 
+When executing qemu, don't forget to point to tsan glib:
+
+.. code::
+
+   $ glib_dir=/path/to/glib
+   $ export 
LD_LIBRARY_PATH=$glib_dir/build/gio:$glib_dir/build/glib:$glib_dir/build/gmodule:$glib_dir/build/gobject:$glib_dir/build/gthread
+   # check correct version is used
+   $ ldd build/qemu-x86_64 | grep glib
+   $ qemu-system-x86_64 ...
+
 The runtime behavior of TSAN is controlled by the TSAN_OPTIONS environment
 variable.
 
-- 
2.39.2