RFR: 8266310: deadlock while loading the JNI code

[David Holmes]

On 14/05/2021 7:20 am, Mandy Chung wrote:
> 
> 
> On 5/13/21 6:05 AM, David Holmes wrote:
>> Not every problem has a solution :) If JNI_OnLoad has to execute 
>> atomically with respect to loading a library then there will always be 
>> a deadlock potential. The only complete solution would not hold a lock 
>> while JNI_OnLoad is executed, but that completely changes the 
>> semantics of native library loading. 
> 
> I have been giving some thought on this issue.  I agree with David that 
> we should look into a solution not holding a lock while JNI_OnLoad is 
> executed.  It might be possible to put all threads that trying to load 
> the same native library that is being loaded to wait and only one thread 
> is loading it and executing JNI_OnLoad (e.g. add a state in 
> NativeLibrary to indicate it is being loaded, already loaded, being 
> unloaded).  I haven't had the cycle to think through it in details though.

Any mechanism that blocks threads from accessing the library while 
another thread is performing JNI_OnLoad, suffers from the same deadlock 
problem.

David

> Mandy