[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PATCH v2 7/9] util/qht: atomically set b->hashes
From: |
Alex Bennée |
Subject: |
[Qemu-devel] [PATCH v2 7/9] util/qht: atomically set b->hashes |
Date: |
Thu, 22 Sep 2016 11:13:14 +0100 |
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 <address@hidden>
---
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
- [Qemu-devel] [PATCH v2 4/9] seqlock: use atomic writes for the sequence, (continued)
- [Qemu-devel] [PATCH v2 4/9] seqlock: use atomic writes for the sequence, Alex Bennée, 2016/09/22
- [Qemu-devel] [PATCH v2 6/9] cpu: atomically modify cpu->exit_request, Alex Bennée, 2016/09/22
- [Qemu-devel] [PATCH v2 3/9] new: blacklist.tsan, Alex Bennée, 2016/09/22
- [Qemu-devel] [PATCH v2 8/9] qga/command: use QEMU atomic primitives, Alex Bennée, 2016/09/22
- [Qemu-devel] [PATCH v2 5/9] qom/object: update class cache atomically, Alex Bennée, 2016/09/22
- [Qemu-devel] [PATCH v2 9/9] .travis.yml: add gcc sanitizer build, Alex Bennée, 2016/09/22
- [Qemu-devel] [PATCH v2 7/9] util/qht: atomically set b->hashes,
Alex Bennée <=
- Re: [Qemu-devel] [PATCH v2 0/9] A couple of fixes for ThreadSanitizer, Paolo Bonzini, 2016/09/30