MDL-65072 core_lock: Locks with a zero timeout return asap

lib/classes/lock/db_record_lock_factory.php

@@ -146,7 +146,7 @@ class db_record_lock_factory implements lock_factory {
             $countparams = array('owner' => $token, 'resourcekey' => $resource);
             $result = $this->db->count_records('lock_db', $countparams);
             $locked = $result === 1;
-            if (!$locked) {
+            if (!$locked && $timeout > 0) {
                 usleep(rand(10000, 250000)); // Sleep between 10 and 250 milliseconds.
             }
             // Try until the giveup time.

lib/classes/lock/file_lock_factory.php

@@ -152,7 +152,7 @@ class file_lock_factory implements lock_factory {
             // Will block on windows. So sad.
             $wouldblock = false;
             $locked = flock($filehandle, LOCK_EX | LOCK_NB, $wouldblock);
-            if (!$locked && $wouldblock) {
+            if (!$locked && $wouldblock && $timeout > 0) {
                 usleep(rand(10000, 250000)); // Sleep between 10 and 250 milliseconds.
             }
             // Try until the giveup time.

lib/classes/lock/postgres_lock_factory.php

@@ -188,7 +188,7 @@ class postgres_lock_factory implements lock_factory {
         do {
             $result = $this->db->get_record_sql('SELECT pg_try_advisory_lock(:locktype, :token) AS locked', $params);
             $locked = $result->locked === 't';
-            if (!$locked) {
+            if (!$locked && $timeout > 0) {
                 usleep(rand(10000, 250000)); // Sleep between 10 and 250 milliseconds.
             }
             // Try until the giveup time.