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[2001:4830:134:3::11]) by mx.google.com with ESMTPS id o63si19473723qkb.89.2016.09.19.08.59.51 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 19 Sep 2016 08:59:51 -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]:56374 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bm0z1-0001lw-2Q for patch@linaro.org; Mon, 19 Sep 2016 11:59:51 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52982) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bm0sR-0005As-Ro for qemu-devel@nongnu.org; Mon, 19 Sep 2016 11:53:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bm0sO-0005AZ-IB for qemu-devel@nongnu.org; Mon, 19 Sep 2016 11:53:03 -0400 Received: from mail-wm0-f42.google.com ([74.125.82.42]:34915) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bm0sO-0005AS-By for qemu-devel@nongnu.org; Mon, 19 Sep 2016 11:53:00 -0400 Received: by mail-wm0-f42.google.com with SMTP id l132so158761392wmf.0 for ; Mon, 19 Sep 2016 08:53:00 -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=y+j0fGJWMjYzmOp/E5CyC6/pNa93uKvcX7Rr3TfQ4tY=; b=Po+y11PVnrennt9OQhNCWmrZgbbDTO+6zzvs0hbygMiTHJOYEfaZSdtodIGOt8vJSu MA0NjwWzrPRkNeYUL+WXetOlU1NuL0/ACqDkSUdo9UhXxOVtGwPjtmnDTMJUS+5JdOW1 eWIib038jjmJjnONqsbqEU1tiipo+swtUQZkM= 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=y+j0fGJWMjYzmOp/E5CyC6/pNa93uKvcX7Rr3TfQ4tY=; b=AKSWw9vf04KVjV3WyXHqjoEUqQxB223E2bg/fkrTN8FwLEBz88Fjmypz4KGxC5w73h MYRLLuVkHAET3mzY5ki1s1zMwVpXYHzpb2EUFRUyZ5MeoGA6B2AGwTXaIUZLUs9lP/NN c/pNLuJq9JwXTyvkYRHjACBNOi2vkJs0psrQvkKaLoWnMVbR1pAgDylGDFrRjzSje8ey CK13dfQmewYBQ3SHTS+DEXrmrYbCOTk7iiNkHzDD2U3G0iezTmZ49d1jk6BbI8sLXK0S WLAYJEdV4eZiwlEKQ/TphYf8tWZ674LU0TGxhvaY53xSyJXgMtqdxC82F9C3S5fckF9W q+Mg== X-Gm-Message-State: AE9vXwPYVEGWg7nwBqQb3w9FJ1/l2TNk8yZR8NtMRXjQeYBfrryYCwVQpJ0N8Og+JU1oK1u3 X-Received: by 10.28.46.204 with SMTP id u195mr10707944wmu.57.1474300319530; Mon, 19 Sep 2016 08:51:59 -0700 (PDT) Received: from zen.linaro.local ([81.128.185.34]) by smtp.gmail.com with ESMTPSA id r8sm23767099wjs.22.2016.09.19.08.51.55 (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 BCB023E0648; 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 16:51:38 +0100 Message-Id: <20160919155139.28371-8-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: 74.125.82.42 Subject: [Qemu-devel] [RFC 7/8] util/qht: atomically set b->hashes 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?= , fred.konrad@greensocs.com Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: "Qemu-devel" ThreadSanitizer detects a possible race between reading/writing the hashes. As ordering semantics are already documented for qht we just need to ensure a race can't tear the hash value so we can use the relaxed atomic_set/read functions. Signed-off-by: Alex Bennée --- util/qht.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) -- 2.9.3 diff --git a/util/qht.c b/util/qht.c index 16a8d79..571639d 100644 --- a/util/qht.c +++ b/util/qht.c @@ -379,7 +379,7 @@ static void qht_bucket_reset__locked(struct qht_bucket *head) if (b->pointers[i] == NULL) { goto done; } - b->hashes[i] = 0; + atomic_set(&b->hashes[i], 0); atomic_set(&b->pointers[i], NULL); } b = b->next; @@ -444,7 +444,7 @@ void *qht_do_lookup(struct qht_bucket *head, qht_lookup_func_t func, do { for (i = 0; i < QHT_BUCKET_ENTRIES; i++) { - if (b->hashes[i] == hash) { + if (atomic_read(&b->hashes[i]) == hash) { /* The pointer is dereferenced before seqlock_read_retry, * so (unlike qht_insert__locked) we need to use * atomic_rcu_read here. @@ -538,8 +538,8 @@ static bool qht_insert__locked(struct qht *ht, struct qht_map *map, if (new) { atomic_rcu_set(&prev->next, b); } - b->hashes[i] = hash; /* smp_wmb() implicit in seqlock_write_begin. */ + atomic_set(&b->hashes[i], hash); atomic_set(&b->pointers[i], p); seqlock_write_end(&head->sequence); return true; @@ -607,10 +607,10 @@ qht_entry_move(struct qht_bucket *to, int i, struct qht_bucket *from, int j) qht_debug_assert(to->pointers[i]); qht_debug_assert(from->pointers[j]); - to->hashes[i] = from->hashes[j]; + atomic_set(&to->hashes[i], from->hashes[j]); atomic_set(&to->pointers[i], from->pointers[j]); - from->hashes[j] = 0; + atomic_set(&from->hashes[j], 0); atomic_set(&from->pointers[j], NULL); }