From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-2.7 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,RCVD_IN_SORBS_SPAM, RP_MATCHES_RCVD shortcircuit=no autolearn=no autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 2E976208B8 for ; Tue, 15 Aug 2017 12:54:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753025AbdHOMyF (ORCPT ); Tue, 15 Aug 2017 08:54:05 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:33695 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752964AbdHOMxm (ORCPT ); Tue, 15 Aug 2017 08:53:42 -0400 Received: by mail-wm0-f66.google.com with SMTP id q189so1380150wmd.0 for ; Tue, 15 Aug 2017 05:53:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:subject:date:message-id:in-reply-to:references:mime-version :content-transfer-encoding; bh=cHOMhsGcxImmF3Ces93ygdNbf7D/5+C/YRAoD2rni4k=; b=hDIwYMix0gmXWT1D3pruV6RBgets1ZZLMYGSvd+abdenoFyariHqGWQb9HTe8DKtTu nKj0JZn9skIwp8i5Kr5ZWzmORBVyzHtHNnnfVay1ayoBwIWUKd+So0Yp+feiab+ZqZ37 8ZkIAnHeiTeZ4fUV3fr2ZV5xSTNIrQ907+K2LneqKldeLFv5Fbf8fiu9C2IhppiL1giN P9Wzd+3PgBsi+juigYM0WUW7JYtq725ekc6Gzqh+LO/j1R6yjkwRN4KKRgNGyDkhcB7i xPpDu0wmhNDhsIIntQk/zW63RbpKIQdk1e/6lDaY/CoRbAXrN7MvYO1SUGJgroGHq2VZ LFOg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=cHOMhsGcxImmF3Ces93ygdNbf7D/5+C/YRAoD2rni4k=; b=UJQdSMkhblHFq5/1R4HTOWvr8ThZeaMEHbcw3d9MbUIMup36J5GIQqFgfvHEKZDPK5 C5qyc8sVXMy6csc9CqQS2UYBmF0j5RWp6JSja1nSPtFSN48H3cTuahuCcbqzO/WFLIVR MYS9mlTWSv03a9wmh7u8EWRaaaQN84gMz+AMPBiYMbMWMudN1mMEONU7woZc3kg27o6a fme/OiXDsfItYnlJqicIo0iAOqL89Daudd4nyekV2krqVeuGGcq94SnWv4gxrJwF6wZJ 7s2d3c+wjTRaS95RNkOpvPvxAvWOTcuv8p4ScSX5L/0eiyV6MksM/47yS7j7diyvocs+ 9pCw== X-Gm-Message-State: AHYfb5iG6brys7yFS3+nNGWzVyPfE4BqEv5+hlgWF4IGGZ0w1p/AylTu zq/UUsZrZNb1A5zs X-Received: by 10.28.88.82 with SMTP id m79mr1372265wmb.52.1502801620800; Tue, 15 Aug 2017 05:53:40 -0700 (PDT) Received: from localhost.localdomain ([2a02:aa16:5782:c100:1208:b1ff:fee6:d811]) by smtp.gmail.com with ESMTPSA id k14sm4006617wrg.11.2017.08.15.05.53.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 15 Aug 2017 05:53:40 -0700 (PDT) From: =?UTF-8?q?Martin=20=C3=85gren?= To: git@vger.kernel.org Subject: [PATCH 4/5] strbuf_reset: don't write to slopbuf with ThreadSanitizer Date: Tue, 15 Aug 2017 14:53:04 +0200 Message-Id: <931ffb00319f40e3c9e099f17eeae6a0c1de41ea.1502780344.git.martin.agren@gmail.com> X-Mailer: git-send-email 2.14.1.151.gdfeca7a7e In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org If two threads have one freshly initialized string buffer each and call strbuf_reset on them at roughly the same time, both threads will be writing a '\0' to strbuf_slopbuf. That is not a problem in practice since it doesn't matter in which order the writes happen. But ThreadSanitizer will consider this a race. When compiling with GIT_THREAD_SANITIZER, avoid writing to strbuf_slopbuf. Let's instead assert on the first byte of strbuf_slopbuf being '\0', since it ensures the promised invariant of "buf[len] == '\0'". (Writing to strbuf_slopbuf is normally bad, but could become even more bad if we stop covering it up in strbuf_reset.) Signed-off-by: Martin Ågren --- strbuf.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/strbuf.h b/strbuf.h index e705b94db..295654d39 100644 --- a/strbuf.h +++ b/strbuf.h @@ -153,7 +153,19 @@ static inline void strbuf_setlen(struct strbuf *sb, size_t len) /** * Empty the buffer by setting the size of it to zero. */ +#ifdef GIT_THREAD_SANITIZER +#define strbuf_reset(sb) \ + do { \ + struct strbuf *_sb = sb; \ + _sb->len = 0; \ + if (_sb->buf == strbuf_slopbuf) \ + assert(!strbuf_slopbuf[0]); \ + else \ + _sb->buf[0] = '\0'; \ + } while (0) +#else #define strbuf_reset(sb) strbuf_setlen(sb, 0) +#endif /** -- 2.14.1.151.gdfeca7a7e