[ovs-dev] [PATCHv2 1/3] revalidator: Refactor ukey creation/lookup.
Joe Stringer
joestringer at nicira.com
Wed Jun 4 01:59:23 UTC 2014
This patch refactors the code around ukey creation and lookup to
simplify the code for callers. A new function ukey_acquire() combines
these functions and attempts to acquire a lock on the ukey. Failure to
acquire a lock on the ukey is usually a sign that another thread is
handling the same flow concurrently, which means the flow does not need
to be handled anyway.
Signed-off-by: Joe Stringer <joestringer at nicira.com>
---
v2: Make ukey_create() return the ukey locked.
Rearrange the logic in ukey_acquire().
---
ofproto/ofproto-dpif-upcall.c | 95 +++++++++++++++++++----------------------
1 file changed, 43 insertions(+), 52 deletions(-)
diff --git a/ofproto/ofproto-dpif-upcall.c b/ofproto/ofproto-dpif-upcall.c
index 9d48e98..3a75690 100644
--- a/ofproto/ofproto-dpif-upcall.c
+++ b/ofproto/ofproto-dpif-upcall.c
@@ -216,6 +216,12 @@ static void upcall_unixctl_set_flow_limit(struct unixctl_conn *conn, int argc,
static struct udpif_key *ukey_create(const struct nlattr *key, size_t key_len,
long long int used);
+static struct udpif_key *ukey_lookup(struct udpif *udpif,
+ const struct nlattr *key, size_t key_len,
+ uint32_t hash);
+static bool ukey_acquire(struct udpif *udpif, const struct nlattr *key,
+ size_t key_len, long long int used,
+ struct udpif_key **result);
static void ukey_delete(struct revalidator *, struct udpif_key *);
static atomic_bool enable_megaflows = ATOMIC_VAR_INIT(true);
@@ -983,8 +989,9 @@ handle_upcalls(struct handler *handler, struct upcall *upcalls,
/* Must be called with udpif->ukeys[hash % udpif->n_revalidators].mutex. */
static struct udpif_key *
-ukey_lookup__(struct udpif *udpif, const struct nlattr *key, size_t key_len,
- uint32_t hash)
+ukey_lookup(struct udpif *udpif, const struct nlattr *key, size_t key_len,
+ uint32_t hash)
+ OVS_REQUIRES(udpif->ukeys->mutex)
{
struct udpif_key *ukey;
struct hmap *hmap = &udpif->ukeys[hash % udpif->n_revalidators].hmap;
@@ -997,26 +1004,15 @@ ukey_lookup__(struct udpif *udpif, const struct nlattr *key, size_t key_len,
return NULL;
}
-static struct udpif_key *
-ukey_lookup(struct udpif *udpif, const struct nlattr *key, size_t key_len,
- uint32_t hash)
-{
- struct udpif_key *ukey;
- uint32_t idx = hash % udpif->n_revalidators;
-
- ovs_mutex_lock(&udpif->ukeys[idx].mutex);
- ukey = ukey_lookup__(udpif, key, key_len, hash);
- ovs_mutex_unlock(&udpif->ukeys[idx].mutex);
-
- return ukey;
-}
-
+/* Creates a ukey for 'key' and 'key_len', returning it with ukey->mutex in
+ * a locked state. */
static struct udpif_key *
ukey_create(const struct nlattr *key, size_t key_len, long long int used)
+ OVS_NO_THREAD_SAFETY_ANALYSIS
{
struct udpif_key *ukey = xmalloc(sizeof *ukey);
- ovs_mutex_init(&ukey->mutex);
+ ovs_mutex_init(&ukey->mutex);
ukey->key = (struct nlattr *) &ukey->key_buf;
memcpy(&ukey->key_buf, key, key_len);
ukey->key_len = key_len;
@@ -1027,33 +1023,44 @@ ukey_create(const struct nlattr *key, size_t key_len, long long int used)
ukey->created = used ? used : time_msec();
memset(&ukey->stats, 0, sizeof ukey->stats);
ukey->xcache = NULL;
- ovs_mutex_unlock(&ukey->mutex);
return ukey;
}
-/* Checks for a ukey in 'udpif->ukeys' with the same 'ukey->key' and 'hash',
- * and inserts 'ukey' if it does not exist.
+/* Searches for a ukey in 'udpif->ukeys' that matches 'key' and 'key_len' and
+ * attempts to lock the ukey. If the ukey does not exist, create it.
*
- * Returns true if 'ukey' was inserted into 'udpif->ukeys', false otherwise. */
+ * Returns true on success, setting *result to the matching ukey and returning
+ * it in a locked state. Otherwise, returns false and clears *result. */
static bool
-udpif_insert_ukey(struct udpif *udpif, struct udpif_key *ukey, uint32_t hash)
+ukey_acquire(struct udpif *udpif, const struct nlattr *key, size_t key_len,
+ long long int used, struct udpif_key **result)
+ OVS_TRY_LOCK(true, (*result)->mutex)
{
- struct udpif_key *duplicate;
- uint32_t idx = hash % udpif->n_revalidators;
- bool ok;
+ struct udpif_key *ukey;
+ uint32_t hash, idx;
+ bool locked = false;
+
+ hash = hash_bytes(key, key_len, udpif->secret);
+ idx = hash % udpif->n_revalidators;
ovs_mutex_lock(&udpif->ukeys[idx].mutex);
- duplicate = ukey_lookup__(udpif, ukey->key, ukey->key_len, hash);
- if (duplicate) {
- ok = false;
- } else {
+ ukey = ukey_lookup(udpif, key, key_len, hash);
+ if (!ukey) {
+ ukey = ukey_create(key, key_len, used);
hmap_insert(&udpif->ukeys[idx].hmap, &ukey->hmap_node, hash);
- ok = true;
+ locked = true;
+ } else if (!ovs_mutex_trylock(&ukey->mutex)) {
+ locked = true;
}
ovs_mutex_unlock(&udpif->ukeys[idx].mutex);
- return ok;
+ if (locked) {
+ *result = ukey;
+ } else {
+ *result = NULL;
+ }
+ return locked;
}
static void
@@ -1362,29 +1369,13 @@ revalidate(struct revalidator *revalidator)
for (f = flows; f < &flows[n_dumped]; f++) {
long long int used = f->stats.used;
- uint32_t hash = hash_bytes(f->key, f->key_len, udpif->secret);
- struct udpif_key *ukey = ukey_lookup(udpif, f->key, f->key_len,
- hash);
+ struct udpif_key *ukey;
bool already_dumped, mark;
- if (!ukey) {
- ukey = ukey_create(f->key, f->key_len, used);
- if (!udpif_insert_ukey(udpif, ukey, hash)) {
- /* The same ukey has already been created. This means that
- * another revalidator is processing this flow
- * concurrently, so don't bother processing it. */
- COVERAGE_INC(upcall_duplicate_flow);
- ukey_delete(NULL, ukey);
- continue;
- }
- }
-
- if (ovs_mutex_trylock(&ukey->mutex)) {
- /* The flow has been dumped, and is being handled by another
- * revalidator concurrently. This can occasionally occur if the
- * datapath is changed in the middle of a flow dump. Rather
- * than perform the same work twice, skip the flow this time.
- */
+ if (!ukey_acquire(udpif, f->key, f->key_len, used, &ukey)) {
+ /* We couldn't acquire the ukey. This means that
+ * another revalidator is processing this flow
+ * concurrently, so don't bother processing it. */
COVERAGE_INC(upcall_duplicate_flow);
continue;
}
--
1.7.10.4
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