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[2001:4830:134:3::11]) by mx.google.com with ESMTPS id q36si18293259qtd.64.2016.09.19.08.55.30 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 19 Sep 2016 08:55:30 -0700 (PDT) Received-SPF: pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 2001:4830:134:3::11 as permitted sender) client-ip=2001:4830:134:3::11; Authentication-Results: mx.google.com; dkim=fail header.i=@linaro.org; spf=pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 2001:4830:134:3::11 as permitted sender) smtp.mailfrom=qemu-devel-bounces+patch=linaro.org@nongnu.org; dmarc=fail (p=NONE dis=NONE) header.from=linaro.org Received: from localhost ([::1]:56346 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bm0uo-0006NA-En for patch@linaro.org; Mon, 19 Sep 2016 11:55:30 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52967) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bm0sR-0005AE-2w for qemu-devel@nongnu.org; Mon, 19 Sep 2016 11:53:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bm0sN-0005A7-LA for qemu-devel@nongnu.org; Mon, 19 Sep 2016 11:53:03 -0400 Received: from mail-lf0-f41.google.com ([209.85.215.41]:33751) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bm0sN-00059k-Dh for qemu-devel@nongnu.org; Mon, 19 Sep 2016 11:52:59 -0400 Received: by mail-lf0-f41.google.com with SMTP id h127so117158447lfh.0 for ; Mon, 19 Sep 2016 08:52:59 -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=ow6+kXvOG3CxiCi3ISWf9FZeDiAhd15FNptkVAYX228=; b=khg3+fx5uJeKQuvcnMMtcO/z5iWZ/j2DxDbeBHQ0GWSjkYpE5hEYcV44QbkNTPSu3k xI0A1BRI+VVk4DdHvjbhGV6gMrow9iWd1ZHSowdrOr9IwtpTwsTdxEkIDOZZGzKJC5uP cFvC3Z8kKQxWR4DtRjnqsTH2CyWKsMRIL/tu0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=ow6+kXvOG3CxiCi3ISWf9FZeDiAhd15FNptkVAYX228=; b=csg+CtkfC50Co3DaP0Nd3y0CLD8jDsT1+RQVmdHQrq45NX0JPTXG2dzDRUKEOmXHHG SDVaGdZwTrQzTcSP9OujQMDsL2ILX7Nvk9w4HIQ/NRdQin/dVyt3PKm9Z7xbX5ocPy/G wPvRS63dzipqwL88uB4d06vqqDIxAyDuwyoYFYaQRuioeVS9m4WtkppXtQM53LiXBzkD k7u/G9zvlz04S5G3MsdXDsK4t6eblLPLYeYx6elM0Z5dqDYdheeXG2j7AastXxGbDpUO hbJ4AkzNVaV1jYh/bUxm1p8aV8VpbBtKbgYFudCm8pliMV8oZNqOjdjJsNCWubSDrBvE oBTw== X-Gm-Message-State: AE9vXwMBL2QwoXqWkJbe6vk8ERbVCZhbUexz3i1U+WDVf/KYDOY065F7EPpPVg6DjqJiep20 X-Received: by 10.194.149.102 with SMTP id tz6mr24145289wjb.154.1474300318189; Mon, 19 Sep 2016 08:51:58 -0700 (PDT) Received: from zen.linaro.local ([81.128.185.34]) by smtp.gmail.com with ESMTPSA id e5sm22732015wma.13.2016.09.19.08.51.55 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 19 Sep 2016 08:51:56 -0700 (PDT) Received: from zen.linaroharston (localhost [127.0.0.1]) by zen.linaro.local (Postfix) with ESMTP id 980583E063E; Mon, 19 Sep 2016 16:51:53 +0100 (BST) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= To: qemu-devel@nongnu.org, pbonzini@redhat.com, cota@braap.org, stefanha@redhat.com, kwolf@redhat.com Date: Mon, 19 Sep 2016 16:51:36 +0100 Message-Id: <20160919155139.28371-6-alex.bennee@linaro.org> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20160919155139.28371-1-alex.bennee@linaro.org> References: <20160919155139.28371-1-alex.bennee@linaro.org> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.85.215.41 Subject: [Qemu-devel] [RFC 5/8] qom/object: update class cache atomically X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mttcg@listserver.greensocs.com, peter.maydell@linaro.org, claudio.fontana@huawei.com, nikunj@linux.vnet.ibm.com, jan.kiszka@siemens.com, mark.burton@greensocs.com, a.rigo@virtualopensystems.com, serge.fdrv@gmail.com, bobby.prani@gmail.com, rth@twiddle.net, =?UTF-8?q?Alex=20Benn=C3=A9e?= , =?UTF-8?q?Andreas=20F=C3=A4rber?= , fred.konrad@greensocs.com Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: "Qemu-devel" The idiom CPU_GET_CLASS(cpu) is fairly extensively used in various threads and trips of ThreadSanitizer due to the fact it updates obj->class->object_cast_cache behind the scenes. As this is just a fast-path cache there is no need to lock updates just ensure that we don't get torn-updates from two racing lookups. While this is unlikely on x86 we use the plain atomic_read/set primitives to make this explicit and keep the sanitizer happy. Signed-off-by: Alex Bennée --- qom/object.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) -- 2.9.3 diff --git a/qom/object.c b/qom/object.c index 8166b7d..7a05e35 100644 --- a/qom/object.c +++ b/qom/object.c @@ -614,7 +614,7 @@ Object *object_dynamic_cast_assert(Object *obj, const char *typename, Object *inst; for (i = 0; obj && i < OBJECT_CLASS_CAST_CACHE; i++) { - if (obj->class->object_cast_cache[i] == typename) { + if (atomic_read(&obj->class->object_cast_cache[i]) == typename) { goto out; } } @@ -631,10 +631,10 @@ Object *object_dynamic_cast_assert(Object *obj, const char *typename, if (obj && obj == inst) { for (i = 1; i < OBJECT_CLASS_CAST_CACHE; i++) { - obj->class->object_cast_cache[i - 1] = - obj->class->object_cast_cache[i]; + atomic_set(&obj->class->object_cast_cache[i - 1], + atomic_read(&obj->class->object_cast_cache[i])); } - obj->class->object_cast_cache[i - 1] = typename; + atomic_set(&obj->class->object_cast_cache[i - 1], typename); } out: @@ -704,7 +704,7 @@ ObjectClass *object_class_dynamic_cast_assert(ObjectClass *class, int i; for (i = 0; class && i < OBJECT_CLASS_CAST_CACHE; i++) { - if (class->class_cast_cache[i] == typename) { + if (atomic_read(&class->class_cast_cache[i]) == typename) { ret = class; goto out; } @@ -725,9 +725,10 @@ ObjectClass *object_class_dynamic_cast_assert(ObjectClass *class, #ifdef CONFIG_QOM_CAST_DEBUG if (class && ret == class) { for (i = 1; i < OBJECT_CLASS_CAST_CACHE; i++) { - class->class_cast_cache[i - 1] = class->class_cast_cache[i]; + atomic_set(&class->class_cast_cache[i - 1], + atomic_read(&class->class_cast_cache[i])); } - class->class_cast_cache[i - 1] = typename; + atomic_set(&class->class_cast_cache[i - 1], typename); } out: #endif