**980+ threads** were blocked at `OgnlRuntime.invokeMethod` with the state `BLOCKED (on object monitor)`, waiting to lock `java.lang.reflect.Method` objects.

[fanzhongwei]

Fix: Reduce thread blocking by double null check instead of synchronizing on Method object #521

We observed severe thread blocking issues in production: 980+ threads were blocked at OgnlRuntime.invokeMethod with the state BLOCKED (on object monitor), waiting to lock java.lang.reflect.Method objects.

# 980 threads blocked
"default-17571" #91915 prio=5 os_prio=0 tid=0x00007f7b7c05d800 nid=0x167f9 waiting for monitor entry [0x00007f757f772000]
   java.lang.Thread.State: BLOCKED (on object monitor)
	at org.apache.ibatis.ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:1151)
	- waiting to lock <0x00000004a55aaf48> (a java.lang.reflect.Method)
	at org.apache.ibatis.ognl.OgnlRuntime.getMethodValue(OgnlRuntime.java:2146)
	at org.apache.ibatis.ognl.ObjectPropertyAccessor.getPossibleProperty(ObjectPropertyAccessor.java:66)
	at org.apache.ibatis.ognl.ObjectPropertyAccessor.getProperty(ObjectPropertyAccessor.java:160)
	at org.apache.ibatis.ognl.OgnlRuntime.getProperty(OgnlRuntime.java:3356)
	...

# got method lock thread
"HSFBizProcessor-DEFAULT-6-thread-5179" #90650 daemon prio=10 os_prio=0 tid=0x00007f794c319000 nid=0x16214 waiting for monitor entry [0x00007f758366e000]
   java.lang.Thread.State: BLOCKED (on object monitor)
	at org.apache.ibatis.ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:1151)
	- locked <0x00000004a55aaf48> (a java.lang.reflect.Method)
	at org.apache.ibatis.ognl.OgnlRuntime.getMethodValue(OgnlRuntime.java:2146)
	at org.apache.ibatis.ognl.ObjectPropertyAccessor.getPossibleProperty(ObjectPropertyAccessor.java:66)
	at org.apache.ibatis.ognl.ObjectPropertyAccessor.getProperty(ObjectPropertyAccessor.java:160)
	at org.apache.ibatis.ognl.OgnlRuntime.getProperty(OgnlRuntime.java:3356)
	...

Root cause:

• Direct synchronization on Method objects leads to heavy thread contention — all threads competing to execute method access checks must wait for the same Method monitor, which severely degrades system concurrency and performance.

[lukaszlenart]

Included in 3.4.10 release