[Bugfix] Fix write-through events not processed when scheduler is idle (#20560)

python/sglang/srt/managers/scheduler.py

@@ -2145,6 +2145,9 @@ class Scheduler(
             for req in ready_grammar_requests:
                 self._add_request_to_queue(req)
 
+        if self.enable_hierarchical_cache:
+            self.tree_cache.check_hicache_events()
+
         if self.enable_priority_preemption:
             # Reset batch_is_full to try preemption with a prefill adder.
             self.running_batch.batch_is_full = False
@@ -2169,9 +2172,6 @@ class Scheduler(
             self.running_batch.batch_is_full = True
             return None
 
-        if self.enable_hierarchical_cache:
-            self.tree_cache.check_hicache_events()
-
         # Get priority queue
         self.policy.calc_priority(self.waiting_queue, self.running_batch)