System.exit deadlock if called within a hook

[remi.catherinot at orange.com]

Ok, you're right that it can raise an exception when the calling thread does not have the security privileges needed. But what if it had them ? Right now the deadlock comes from the fact is doesn't got back to the caller with an exception and doesn't end the current thread. My 1st proposal was to have a way to end the current thread. If you think that is not acceptable and prefer the exception solution, then something like throw new IllegalStateException("Shutdown in progress") which is already used when adding new hooks while shutting down and adjust the System.exit method documentation accordingly (might be dangerous since it "breaks" actual documented and implemented contract, might be too heavy for a change).

First things first : do you think this is an issue the JVM has to solve (either using a destroy-current-thread solution, or a throw-IllegalStateException one), or do you think this was a hook misuse and maybe would only need maybe a clearer warning in the hooks's documentation, or do you think we keep everything as it is because I should have guessed better reading the actual documentation �� ?

My demo code is simple, but the environment in which it happened and being able to understand the jstack output with lots of frameworks hooking here and there plus some uncaught exception hanlders kicking in was really really hard. In my case I ended up having a hook to run a delayed Runtime.halt call, which more feels like a JVM workaround rather than a framework workaround.

Regards,


Orange Restricted

-----Message d'origine-----
De : David Lloyd <david.lloyd at redhat.com> 
Envoyé : lundi 25 avril 2022 15:41
À : CATHERINOT Rémi DTSI/PFS <remi.catherinot at orange.com>
Cc : core-libs-dev at openjdk.java.net
Objet : Re: System.exit deadlock if called within a hook

On Mon, Apr 25, 2022 at 8:09 AM <remi.catherinot at orange.com> wrote:
> because it would still run finally blocks, which cannot happen for no 
> return methods like System.exit and Runtime.halt

FWIW I don't think this is correct. `exit` and `halt` etc. cannot
*return* but they're definitely allowed to throw an exception (`SecurityException` is presently specified) and thus are allowed to unwind the stack, even through `finally` blocks.

--
- DML • he/him

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