From patchwork Thu Sep 22 10:13:12 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Alex_Benn=C3=A9e?= X-Patchwork-Id: 76740 Delivered-To: patch@linaro.org Received: by 10.140.106.72 with SMTP id d66csp2524311qgf; Thu, 22 Sep 2016 03:50:57 -0700 (PDT) X-Received: by 10.200.38.241 with SMTP id 46mr1187230qtp.135.1474541457025; Thu, 22 Sep 2016 03:50:57 -0700 (PDT) Return-Path: Received: from lists.gnu.org (lists.gnu.org. [2001:4830:134:3::11]) by mx.google.com with ESMTPS id n135si696844qke.65.2016.09.22.03.50.56 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 22 Sep 2016 03:50:57 -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]:37868 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bn1ai-00070o-Hb for patch@linaro.org; Thu, 22 Sep 2016 06:50:56 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50926) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bn11W-000856-C4 for qemu-devel@nongnu.org; Thu, 22 Sep 2016 06:14:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bn11R-0006pG-9u for qemu-devel@nongnu.org; Thu, 22 Sep 2016 06:14:33 -0400 Received: from mail-wm0-f53.google.com ([74.125.82.53]:36726) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bn11R-0006p2-3q for qemu-devel@nongnu.org; Thu, 22 Sep 2016 06:14:29 -0400 Received: by mail-wm0-f53.google.com with SMTP id w84so243502998wmg.1 for ; Thu, 22 Sep 2016 03:14:29 -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=yhvaAqZ0cNUUuSCD9oCQOIEA9BTn7AxIIDqyR2zwNTk=; b=YwpVY7wMaUbV9IXqv0KCHI7HYT9/eRpKCG7n+R1I3pPgOMIrmv4mUSOovODJl7ZL2M FpWclslpUHaeulTep949kN6UVJ/aaVJYuU9g1y0H0alosqnEIn0ppr336ZVB7gt2LWKs pPtQ/RBQ2Ije6X77BbMQj5xW/exUGYSdfWPn4= 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=yhvaAqZ0cNUUuSCD9oCQOIEA9BTn7AxIIDqyR2zwNTk=; b=Rjajm5Fxne6XeMLybZKJGhS/xx/81VI5bDfszn0D6viQiKBPCYdp9BSwudgx43y8YM Q6ctIy3ftrs66TLbuLBqw1ULhb84k87TYMop/C1+u7R78pYekxF87kEKJ0uXS8aIfYAW U0CvMn1wfZtLXpEnr5aYfHdrZXrUHYyCVd5+sHWXNnueYUcnVPyxuzkhFp9zMmfKgm2O 53sy/MqCiLNjYKvZ1ARlb6u1FRXZRYMighf1WuoBp0yuWWSdaiKPgXpwStQC9gp/tSdL IKEps87Qh3LSYqK7SuOBl8QJKIGmGyYb91tEFUqAdsGWFI2fnKzUCRHSc8F5qBrUlJzL 3m6g== X-Gm-Message-State: AA6/9RlF+bPVqbR0ZYLOKOyzb6YRC/haFm9V7A1Jj4mRYjGrmR9/adQ9JNOvhJHjztJv6Qt2 X-Received: by 10.28.228.68 with SMTP id b65mr1621785wmh.124.1474539208413; Thu, 22 Sep 2016 03:13:28 -0700 (PDT) Received: from zen.linaro.local ([81.128.185.34]) by smtp.gmail.com with ESMTPSA id xb6sm1299675wjb.30.2016.09.22.03.13.24 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 22 Sep 2016 03:13:25 -0700 (PDT) Received: from zen.linaroharston (localhost [127.0.0.1]) by zen.linaro.local (Postfix) with ESMTP id CD9F43E02A9; Thu, 22 Sep 2016 11:13:22 +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: Thu, 22 Sep 2016 11:13:12 +0100 Message-Id: <20160922101316.13064-6-alex.bennee@linaro.org> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20160922101316.13064-1-alex.bennee@linaro.org> References: <20160922101316.13064-1-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: 74.125.82.53 Subject: [Qemu-devel] [PATCH v2 5/9] 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 Reviewed-by: Marc-André Lureau --- 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