From patchwork Tue Jun 9 20:07:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Robert Foley X-Patchwork-Id: 11596569 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5B2FF618 for ; Tue, 9 Jun 2020 20:21:25 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 2CC2D206C3 for ; Tue, 9 Jun 2020 20:21:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="RY9HSuxK" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2CC2D206C3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:60550 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jikkO-0004Dr-Gl for patchwork-qemu-devel@patchwork.kernel.org; Tue, 09 Jun 2020 16:21:24 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:59352) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jikZM-0007wu-Tu for qemu-devel@nongnu.org; Tue, 09 Jun 2020 16:10:00 -0400 Received: from mail-pf1-x441.google.com ([2607:f8b0:4864:20::441]:43454) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jikZL-0005cX-T9 for qemu-devel@nongnu.org; Tue, 09 Jun 2020 16:10:00 -0400 Received: by mail-pf1-x441.google.com with SMTP id 23so38713pfw.10 for ; Tue, 09 Jun 2020 13:09:59 -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:in-reply-to:references :mime-version:content-transfer-encoding; bh=zkAx8xWtCWhcEMmU8jAnkCrKBrfEu7h9Ojxrn77WllE=; b=RY9HSuxKrh+3sCVZGVO29aHtQcqu05Ks7BVdJWz6BGcbmrXjcthKCUNBmjXQFQZ1rw gvUaLSY54aJA4LA+m72NIXhgBfOyN8KufeDoEdYyw88z99Ua6y3Cdrz3ipWw5h8ThVe/ tXj43gVefliTzfn95WLeogFT3JB512U8ohSHZK9UNjiyj3eH3b3jKIJnHXc4kTAeJ/SZ VUohOqcs/EA7SMw6LFgYr3tnk4TJ2rCbL8D285xMaAFpx0+bS8aEWpft9kwVc2EnYsom 2cybvXWxHFCmAq4zwZoyOGDKqirVDKeYOguiDcnh11zalctU9OGEFufq2vNwG/ms7Tv7 M6QQ== 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:in-reply-to :references:mime-version:content-transfer-encoding; bh=zkAx8xWtCWhcEMmU8jAnkCrKBrfEu7h9Ojxrn77WllE=; b=pbMZV5u4xKf/mPqrtKje2yVRFnUxfPLuxNgmGiYTTH+WRL1W9juHGMT7jo/NYbBBMI WfWN6TyfQAbdfTuscCDoK0eSuslvphYZBGzzgvbGLvzgjx2hqThszz++Y7Sb+cz1X8gO aKzIBlLqzY48GARPRdHgTM54u450DI7XLfNT7n48OT01n3Rgih37gUM5E0AMTs0JMr8l zH71HIB6A0qjEptHyXgZJw6tzZVNUcDobeDuq0XxOGcObQgUjv9YgQB4i+cZ3inM/iL0 GXKTIMLHbOvBeMevAuO3qCf820g1w4NkSRmKo9VYEpWUCL0hf4AZWXR3n20xOUocysr/ aDiQ== X-Gm-Message-State: AOAM530M13ANuNHdV5mT6SreTXazTzoUICJPMZaQoE+QJLT2FXFd7Rh2 Zzqw0PohZ8Coa4Wy5H1U7s7PEE8XzNJvog== X-Google-Smtp-Source: ABdhPJzbFDhQ1//obqhcgw4mrxhYcS7LcsCDuySrwkybLPcs8s46Y0PK3LkFeG5gHlYlpr3XzDeH5Q== X-Received: by 2002:a62:55c1:: with SMTP id j184mr25464470pfb.240.1591733398111; Tue, 09 Jun 2020 13:09:58 -0700 (PDT) Received: from Rfoley-MA01.hsd1.ma.comcast.net ([2601:199:4480:60c0:1d09:cef2:3b1f:abce]) by smtp.gmail.com with ESMTPSA id n19sm10523374pfu.194.2020.06.09.13.09.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Jun 2020 13:09:57 -0700 (PDT) From: Robert Foley To: qemu-devel@nongnu.org Subject: [PATCH v3 12/13] docs: Added details on TSan to testing.rst Date: Tue, 9 Jun 2020 16:07:37 -0400 Message-Id: <20200609200738.445-13-robert.foley@linaro.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200609200738.445-1-robert.foley@linaro.org> References: <20200609200738.445-1-robert.foley@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::441; envelope-from=robert.foley@linaro.org; helo=mail-pf1-x441.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 Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.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 Reviewed-by: Alex Bennée --- docs/devel/testing.rst | 107 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 107 insertions(+) diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst index 770a987ea4..c1ff24370b 100644 --- a/docs/devel/testing.rst +++ b/docs/devel/testing.rst @@ -397,6 +397,113 @@ 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. + +The test-tsan test will build using TSan and then run make check. + +.. code:: + + make docker-test-tsan@ubuntu2004 + +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_warning + +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 ==========