From patchwork Fri May 29 13:24:38 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Robert Foley X-Patchwork-Id: 1300708 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=linaro.org header.i=@linaro.org header.a=rsa-sha256 header.s=google header.b=blVp3do4; dkim-atps=neutral Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 49YQVF185yz9sSr for ; Fri, 29 May 2020 23:32:37 +1000 (AEST) Received: from localhost ([::1]:50824 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jef7i-00023J-T1 for incoming@patchwork.ozlabs.org; Fri, 29 May 2020 09:32:34 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43118) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jef0P-0006UG-9c for qemu-devel@nongnu.org; Fri, 29 May 2020 09:25:01 -0400 Received: from mail-pj1-x1042.google.com ([2607:f8b0:4864:20::1042]:38833) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jef0O-000452-1n for qemu-devel@nongnu.org; Fri, 29 May 2020 09:25:00 -0400 Received: by mail-pj1-x1042.google.com with SMTP id t8so1329903pju.3 for ; Fri, 29 May 2020 06:24:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id; bh=sMSUvaGVYsjE3AMoDsJ2TYvIyY2QCzLj9JPqQSj65XM=; b=blVp3do4CV99FRaoe/I2mK0lMhr/QDqw7tOHbSmwE1l49yzEd1OEjmeDPW+GiHqY4t XmVs6KUdiHm/mSNfOrKwVmGtHp5lQAPnvtwHr8PnWynmw4bcw5i0+sVSb9ZFpm/x7Wzj /+XKQPOoveaig1DkACYpkceuB9tZdnCGf43BTmZ2PKTgPWmAZ4Mch4AmhQWEGigsPu8U v5mONNo6xjr8LD0U2CG7QN+ANgtUlwFFFtRLNRx4Z+wY7d5sCqPd1lqeiCtd/BH3uLvB cDD2SzbVIFvXi7T1dna8TFRc4fZU9UAJpoJOluUzt6OzJjSKtlC5rJvHJx/mkpOe20vq wWTw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=sMSUvaGVYsjE3AMoDsJ2TYvIyY2QCzLj9JPqQSj65XM=; b=VAHFvDCKunxW9oiCwXbTDFT32Q2T1cB2oa5mwCfaF6wCw2h57cass3gQRmuZ/1GJtB QuA3/LZllQ6mb6FjuFYOlv6rOOWzSxSZibNmwrtEqxDWJmxAGwgE2J3jsICTLaEhaMwr k0mYEQUnQOjsovvhqny6K+WMQi8mDuvpnbyFD0H/uSOLzTseKQzG0hChHS7Sf8Eb43W2 k3KQi4HTVaiBbYjgkD90MZRuQCnTTmqwhkz4YOEhuKU23D7TkA0Hr097i1Erct4UPUe0 3vNXlnyLuyQ1mPfc1IKBqjf/uzrEy2AyPpZB03XYnP+0p9/1MFFV5MwmIoO2d9HYQk7G ljyA== X-Gm-Message-State: AOAM531bs8q21RePaLLU3Ks+CRPzk2AP4P4VyfuyXM038ALnreR1bmGN UYr3t6+7RVwDZOhSIAC5XK23jIJEscz5ng== X-Google-Smtp-Source: ABdhPJwNey+wTHvYnJiz9mViYrjHMUJT9IX1tCPe7df7VpMQam7JThuUQ3qG6K8Qkf8Lu7/YZQvP8g== X-Received: by 2002:a17:90a:ad92:: with SMTP id s18mr9675955pjq.30.1590758698186; Fri, 29 May 2020 06:24:58 -0700 (PDT) Received: from Rfoley-MA01.hsd1.ma.comcast.net ([2601:199:4480:60c0:75ac:d268:da04:dde4]) by smtp.gmail.com with ESMTPSA id bu7sm8370538pjb.41.2020.05.29.06.24.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 May 2020 06:24:57 -0700 (PDT) From: Robert Foley To: qemu-devel@nongnu.org Subject: [PATCH v1 12/12] docs: Added details on TSan to testing.rst Date: Fri, 29 May 2020 09:24:38 -0400 Message-Id: <20200529132438.837-1-robert.foley@linaro.org> X-Mailer: git-send-email 2.17.1 Received-SPF: pass client-ip=2607:f8b0:4864:20::1042; envelope-from=robert.foley@linaro.org; helo=mail-pj1-x1042.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.puhov@linaro.org, cota@braap.org, alex.bennee@linaro.org, robert.foley@linaro.org, stefanha@redhat.com Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" Adds TSan details to testing.rst. This includes background and reference details on TSan, and details on how to build and test with TSan both with and without docker. Signed-off-by: Robert Foley Reviewed-by: Emilio G. Cota --- docs/devel/testing.rst | 113 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 113 insertions(+) diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst index 770a987ea4..17a07ff8c0 100644 --- a/docs/devel/testing.rst +++ b/docs/devel/testing.rst @@ -397,6 +397,119 @@ list is in the ``make docker`` help text. The frequently used ones are: * ``DEBUG=1``: enables debug. See the previous "Debugging a Docker test failure" section. +Thread Sanitizer +================ + +Thread Sanitizer (TSan) is a tool which can detect data races. QEMU supports +building and testing with this tool. + +For more information on TSan: + +https://github.com/google/sanitizers/wiki/ThreadSanitizerCppManual + +Thread Sanitizer in Docker +--------------------------- +TSan is currently supported in the ubuntu2004 docker. + +Just add the TSAN=1 argument to use TSan + +.. code:: + + make docker-test-build@ubuntu2004 TSAN=1 + +or + +.. code:: + + make docker-test-quick@ubuntu2004 TSAN=1 + +TSan warnings under docker are placed in files located at build/tsan/. + +We recommend using DEBUG=1 to allow launching the test from inside the docker, +and to allow review of the warnings generated by TSan. + +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: + +.. code:: + + sed -i 's/^const/static const/g' \ + /usr/lib/llvm-10/lib/clang/10.0.0/include/sanitizer/tsan_interface.h + +To configure the build for TSan: + +.. code:: + + ../configure --enable-tsan --cc=clang-10 --cxx=clang++-10 \ + --disable-werror --extra-cflags="-O0" + +The runtime behavior of TSAN is controlled by the TSAN_OPTIONS environment +variable. + +More information on the TSAN_OPTIONS can be found here: + +https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags + +For example: + +.. code:: + + export TSAN_OPTIONS=suppressions=/tests/tsan/suppressions.tsan \ + detect_deadlocks=false history_size=7 exitcode=0 \ + log_path=/tsan/tsan_warnings.txt + +The above exitcode=0 has TSan continue without error if any warnings are found. +This allows for running the test and then checking the warnings afterwards. +If you want TSan to stop and exit with error on warnings, use exitcode=66. + +TSan Suppressions +----------------- +Keep in mind that for any data race warning, although there might be a data race +detected by TSan, there might be no actual bug here. TSan provides several +different mechanisms for suppressing warnings. In general it is recommended +to fix the code if possible to eliminate the data race rather than suppress +the warning. + +A few important files for suppressing warnings are: + +tests/tsan/suppressions.tsan - Has TSan warnings we wish to suppress at runtime. +The comment on each supression will typically indicate why we are +suppressing it. More information on the file format can be found here: + +https://github.com/google/sanitizers/wiki/ThreadSanitizerSuppressions + +tests/tsan/blacklist.tsan - Has TSan warnings we wish to disable +at compile time for test or debug. +Add flags to configure to enable: + +"--extra-cflags=-fsanitize-blacklist=/tests/tsan/blacklist.tsan" + +More information on the file format can be found here under "Blacklist Format": + +https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags + +TSan Annotations +---------------- +include/qemu/tsan.h defines annotations. See this file for more descriptions +of the annotations themselves. Annotations can be used to suppress +TSan warnings or give TSan more information so that it can detect proper +relationships between accesses of data. + +Annotation examples can be found here: + +https://github.com/llvm/llvm-project/tree/master/compiler-rt/test/tsan/ + +Good files to start with are: annotate_happens_before.cpp and ignore_race.cpp + +The full set of annotations can be found here: + +https://github.com/llvm/llvm-project/blob/master/compiler-rt/lib/tsan/rtl/tsan_interface_ann.cpp + VM testing ==========