From: Numan Siddique <[email protected]>

Its possible for pinctrl handling for DNS packets to be blocked
if the ovn-controller main thread has acquired the dns cache
mutex during the recompute.  This patch improves the DNS packet
handling by using cmap instead of hmap to maintain the dns cache.
With this, there is no need to maintain a mutex.

Suggested-by: Ales Musil <[email protected]>
Signed-off-by: Numan Siddique <[email protected]>
---
 controller/ovn-dns.c | 144 ++++++++++++++++++-------------------------
 1 file changed, 60 insertions(+), 84 deletions(-)

diff --git a/controller/ovn-dns.c b/controller/ovn-dns.c
index 026d9bc647..d488a7d8e4 100644
--- a/controller/ovn-dns.c
+++ b/controller/ovn-dns.c
@@ -18,6 +18,7 @@
 /* OVS includes */
 #include "include/openvswitch/shash.h"
 #include "include/openvswitch/thread.h"
+#include "lib/cmap.h"
 #include "openvswitch/vlog.h"
 
 /* OVN includes. */
@@ -28,7 +29,7 @@ VLOG_DEFINE_THIS_MODULE(ovndns);
 
 /* Internal DNS cache entry for each SB DNS record. */
 struct dns_data {
-    struct hmap_node hmap_node;
+    struct cmap_node cmap_node;
     struct uuid uuid;
     uint64_t *dps;
     size_t n_dps;
@@ -38,114 +39,87 @@ struct dns_data {
 };
 
 /* shash of 'struct dns_data'. */
-static struct hmap dns_cache_ = HMAP_INITIALIZER(&dns_cache_);
-
-/* Mutex to protect dns_cache_. */
-static struct ovs_mutex dns_cache_mutex = OVS_MUTEX_INITIALIZER;
+static struct cmap dns_cache_;
 
 static void update_cache_with_dns_rec(const struct sbrec_dns *,
                                       struct dns_data *,
                                       const struct uuid *uuid,
-                                      struct hmap *dns_cache);
-static struct dns_data *dns_data_find(const struct uuid *uuid);
+                                      struct cmap *dns_cache);
+static struct dns_data *dns_data_find(const struct uuid *uuid,
+                                      const struct cmap *);
 static struct dns_data *dns_data_alloc(struct uuid uuid);
 static void dns_data_destroy(struct dns_data *dns_data);
+static void destroy_dns_cache(struct cmap *dns_cache);
 
 void
 ovn_dns_cache_init(void)
 {
+    cmap_init(&dns_cache_);
 }
 
 void
 ovn_dns_cache_destroy(void)
 {
-    ovs_mutex_lock(&dns_cache_mutex);
-    struct dns_data *dns_data;
-    HMAP_FOR_EACH_POP (dns_data, hmap_node, &dns_cache_) {
-        dns_data_destroy(dns_data);
-    }
-    hmap_destroy(&dns_cache_);
-    ovs_mutex_unlock(&dns_cache_mutex);
+    destroy_dns_cache(&dns_cache_);
+    cmap_destroy(&dns_cache_);
 }
 
 void
 ovn_dns_sync_cache(const struct sbrec_dns_table *dns_table)
 {
-    ovs_mutex_lock(&dns_cache_mutex);
-    struct dns_data *dns_data;
-    HMAP_FOR_EACH (dns_data, hmap_node, &dns_cache_) {
-        dns_data->delete = true;
+    const struct sbrec_dns *sbrec_dns;
+    struct dns_data *existing;
+
+    CMAP_FOR_EACH (existing, cmap_node, &dns_cache_) {
+        existing->delete = true;
     }
 
-    const struct sbrec_dns *sbrec_dns;
     SBREC_DNS_TABLE_FOR_EACH (sbrec_dns, dns_table) {
         const struct uuid *uuid = &sbrec_dns->header_.uuid;
-        dns_data = dns_data_find(uuid);
-        if (!dns_data) {
-            dns_data = dns_data_alloc(*uuid);
-            hmap_insert(&dns_cache_, &dns_data->hmap_node, uuid_hash(uuid));
-        } else {
-            free(dns_data->dps);
-        }
-
-        dns_data->delete = false;
-
-        if (!smap_equal(&dns_data->records, &sbrec_dns->records)) {
-            smap_destroy(&dns_data->records);
-            smap_clone(&dns_data->records, &sbrec_dns->records);
-        }
-
-        if (!smap_equal(&dns_data->options, &sbrec_dns->options)) {
-            smap_destroy(&dns_data->options);
-            smap_clone(&dns_data->options, &sbrec_dns->options);
-        }
-
-        dns_data->n_dps = sbrec_dns->n_datapaths;
-        dns_data->dps = xcalloc(dns_data->n_dps, sizeof(uint64_t));
-        for (size_t i = 0; i < sbrec_dns->n_datapaths; i++) {
-            dns_data->dps[i] = sbrec_dns->datapaths[i]->tunnel_key;
-        }
+        existing = dns_data_find(uuid, &dns_cache_);
+        update_cache_with_dns_rec(sbrec_dns, existing, uuid,
+                                  &dns_cache_);
     }
 
-    HMAP_FOR_EACH_SAFE (dns_data, hmap_node, &dns_cache_) {
-        if (dns_data->delete) {
-            hmap_remove(&dns_cache_, &dns_data->hmap_node);
-            dns_data_destroy(dns_data);
+    CMAP_FOR_EACH (existing, cmap_node, &dns_cache_) {
+        if (existing->delete) {
+            cmap_remove(&dns_cache_, &existing->cmap_node,
+                        uuid_hash(&existing->uuid));
+            dns_data_destroy(existing);
         }
     }
-    ovs_mutex_unlock(&dns_cache_mutex);
 }
 
 void
 ovn_dns_update_cache(const struct sbrec_dns_table *dns_table)
 {
-    ovs_mutex_lock(&dns_cache_mutex);
-
     const struct sbrec_dns *sbrec_dns;
+    struct dns_data *existing;
+
     SBREC_DNS_TABLE_FOR_EACH_TRACKED (sbrec_dns, dns_table) {
         const struct uuid *uuid = &sbrec_dns->header_.uuid;
-        struct dns_data *dns_data = dns_data_find(uuid);
 
-        if (sbrec_dns_is_deleted(sbrec_dns) && dns_data) {
-            hmap_remove(&dns_cache_, &dns_data->hmap_node);
-            dns_data_destroy(dns_data);
+        existing = dns_data_find(uuid, &dns_cache_);
+        if (sbrec_dns_is_deleted(sbrec_dns) && existing) {
+            cmap_remove(&dns_cache_, &existing->cmap_node,
+                        uuid_hash(&existing->uuid));
+            dns_data_destroy(existing);
         } else {
-            update_cache_with_dns_rec(sbrec_dns, dns_data, uuid, &dns_cache_);
+            update_cache_with_dns_rec(sbrec_dns, existing, uuid,
+                                      &dns_cache_);
         }
     }
-
-    ovs_mutex_unlock(&dns_cache_mutex);
 }
 
 const char *
 ovn_dns_lookup(const char *query_name, uint64_t dp_key, bool *ovn_owned)
 {
-    ovs_mutex_lock(&dns_cache_mutex);
+    const char *answer_data = NULL;
+    struct dns_data *dns_data;
 
     *ovn_owned = false;
-    struct dns_data *dns_data;
-    const char *answer_data = NULL;
-    HMAP_FOR_EACH (dns_data, hmap_node, &dns_cache_) {
+
+    CMAP_FOR_EACH (dns_data, cmap_node, &dns_cache_) {
         for (size_t i = 0; i < dns_data->n_dps; i++) {
             if (dns_data->dps[i] == dp_key) {
                 /* DNS records in SBDB are stored in lowercase. Convert to
@@ -167,8 +141,6 @@ ovn_dns_lookup(const char *query_name, uint64_t dp_key, 
bool *ovn_owned)
         }
     }
 
-    ovs_mutex_unlock(&dns_cache_mutex);
-
     return answer_data;
 }
 
@@ -176,40 +148,35 @@ ovn_dns_lookup(const char *query_name, uint64_t dp_key, 
bool *ovn_owned)
 /* Static functions. */
 static void
 update_cache_with_dns_rec(const struct sbrec_dns *sbrec_dns,
-                          struct dns_data *dns_data,
+                          struct dns_data *existing,
                           const struct uuid *uuid,
-                          struct hmap *dns_cache)
+                          struct cmap *dns_cache)
 {
-    if (!dns_data) {
-        dns_data = dns_data_alloc(*uuid);
-        hmap_insert(dns_cache, &dns_data->hmap_node, uuid_hash(uuid));
-    } else {
-        free(dns_data->dps);
-    }
-
-    if (!smap_equal(&dns_data->records, &sbrec_dns->records)) {
-        smap_destroy(&dns_data->records);
-        smap_clone(&dns_data->records, &sbrec_dns->records);
-    }
-
-    if (!smap_equal(&dns_data->options, &sbrec_dns->options)) {
-        smap_destroy(&dns_data->options);
-        smap_clone(&dns_data->options, &sbrec_dns->options);
-    }
+    struct dns_data *dns_data = dns_data_alloc(*uuid);
+    smap_clone(&dns_data->records, &sbrec_dns->records);
+    smap_clone(&dns_data->options, &sbrec_dns->options);
 
     dns_data->n_dps = sbrec_dns->n_datapaths;
     dns_data->dps = xcalloc(dns_data->n_dps, sizeof(uint64_t));
     for (size_t i = 0; i < sbrec_dns->n_datapaths; i++) {
         dns_data->dps[i] = sbrec_dns->datapaths[i]->tunnel_key;
     }
+
+    if (!existing) {
+        cmap_insert(dns_cache, &dns_data->cmap_node, uuid_hash(uuid));
+    } else {
+        cmap_replace(dns_cache, &existing->cmap_node, &dns_data->cmap_node,
+                     uuid_hash(uuid));
+        dns_data_destroy(existing);
+    }
 }
 
 static struct dns_data *
-dns_data_find(const struct uuid *uuid)
+dns_data_find(const struct uuid *uuid, const struct cmap *dns_cache)
 {
     struct dns_data *dns_data;
     size_t hash = uuid_hash(uuid);
-    HMAP_FOR_EACH_WITH_HASH (dns_data, hmap_node, hash, &dns_cache_) {
+    CMAP_FOR_EACH_WITH_HASH (dns_data, cmap_node, hash, dns_cache) {
         if (uuid_equals(&dns_data->uuid, uuid)) {
             return dns_data;
         }
@@ -240,3 +207,12 @@ dns_data_destroy(struct dns_data *dns_data)
     free(dns_data->dps);
     free(dns_data);
 }
+
+static void
+destroy_dns_cache(struct cmap *dns_cache)
+{
+    struct dns_data *dns_data;
+    CMAP_FOR_EACH (dns_data, cmap_node, dns_cache) {
+        dns_data_destroy(dns_data);
+    }
+}
-- 
2.47.1

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