From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50934) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bn11W-00085m-OZ 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 1bn11S-0006pW-12 for qemu-devel@nongnu.org; Thu, 22 Sep 2016 06:14:33 -0400 Received: from mail-wm0-f42.google.com ([74.125.82.42]:38832) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bn11R-0006pO-Qu for qemu-devel@nongnu.org; Thu, 22 Sep 2016 06:14:29 -0400 Received: by mail-wm0-f42.google.com with SMTP id l132so139222450wmf.1 for ; Thu, 22 Sep 2016 03:14:29 -0700 (PDT) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= Date: Thu, 22 Sep 2016 11:13:14 +0100 Message-Id: <20160922101316.13064-8-alex.bennee@linaro.org> In-Reply-To: <20160922101316.13064-1-alex.bennee@linaro.org> References: <20160922101316.13064-1-alex.bennee@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [Qemu-devel] [PATCH v2 7/9] util/qht: atomically set b->hashes List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, pbonzini@redhat.com, cota@braap.org, stefanha@redhat.com, kwolf@redhat.com Cc: mttcg@listserver.greensocs.com, fred.konrad@greensocs.com, a.rigo@virtualopensystems.com, bobby.prani@gmail.com, nikunj@linux.vnet.ibm.com, mark.burton@greensocs.com, jan.kiszka@siemens.com, serge.fdrv@gmail.com, rth@twiddle.net, peter.maydell@linaro.org, claudio.fontana@huawei.com, =?UTF-8?q?Alex=20Benn=C3=A9e?= 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(-) 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); } -- 2.9.3