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lib/classifier: Minimize critical section.

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classifier_find_rule_exactly() only needs the mutex to protect the
list traversal.  Subtables are already RCU protected.

Locking here can be eliminated completely when RCU list is available.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
This commit is contained in:
Jarno Rajahalme
2014-10-14 13:31:48 -07:00
parent 3be1eaee75
commit d2064437e2
1 changed files with 8 additions and 12 deletions
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20
lib/classifier.c
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@@ -114,8 +114,7 @@ cls_match_alloc(struct cls_rule *rule)
}
static struct cls_subtable *find_subtable(const struct classifier *cls,
const struct minimask *)
OVS_REQUIRES(cls->mutex);
const struct minimask *);
static struct cls_subtable *insert_subtable(struct classifier *cls,
const struct minimask *)
OVS_REQUIRES(cls->mutex);
@@ -1090,28 +1089,26 @@ classifier_find_rule_exactly(const struct classifier *cls,
struct cls_match *head, *rule;
struct cls_subtable *subtable;
ovs_mutex_lock(&cls->mutex);
subtable = find_subtable(cls, &target->match.mask);
if (!subtable) {
goto out;
}
/* Skip if there is no hope. */
if (target->priority > subtable->max_priority) {
goto out;
if (!subtable || target->priority > subtable->max_priority) {
return NULL;
}
head = find_equal(subtable, &target->match.flow,
miniflow_hash_in_minimask(&target->match.flow,
&target->match.mask, 0));
/* Use RCU list instead of locking when one is available. */
ovs_mutex_lock(&cls->mutex);
FOR_EACH_RULE_IN_LIST (rule, head) {
if (target->priority >= rule->priority) {
ovs_mutex_unlock(&cls->mutex);
return target->priority == rule->priority ? rule->cls_rule : NULL;
}
}
out:
ovs_mutex_unlock(&cls->mutex);
return NULL;
}
@@ -1339,7 +1336,6 @@ cls_cursor_advance(struct cls_cursor *cursor)
static struct cls_subtable *
find_subtable(const struct classifier *cls, const struct minimask *mask)
OVS_REQUIRES(cls->mutex)
{
struct cls_subtable *subtable;