Improve registering signal handlers in java.lang.Terminator.setup()

[Alan Bateman]

On 07/08/2012 19:07, Neil Richards wrote:
> :
> Digging back into its history, I see that it all stems from running java
> under 'nohup' (e.g. 'nohup java ProgramWithShutdownHooks&').
>
> 'nohup' prevents things being registered against SIGHUP, so trying to do
> so causes an exception to be thrown.
>
> When this happens, the Terminator code currently decides that it
> shouldn't bother trying to register shutdown hooks for SIGINT or SIGTERM
> either.
>
> The result is that shutdown hooks aren't currently run when a java
> process run using 'nohup' is sent a SIGINT or SIGTERM signal, because of
> the code's (false) assumption that a failure to register a handler for
> SIGHUP must mean that the VM is running in -Xrs mode.
>
> I don't think the current observed behaviour in this scenario is either
> expected or desirable.
> It occurs for both J9 and Hotspot (at least, on my Ubuntu box, bash
> shell).
>
> Hope this helps to clarify the scenario.
>
Thanks for helping to clarify what this issue is about. One thing that 
still isn't clear (to me anyway) is whether IAE is really thrown in this 
case. I did a quick test on Ubuntu 12.04:

$ nohup strace -f java Test 2> log &

and in the log I see the sigactions as I expected:

[pid 13829] rt_sigaction(SIGHUP, NULL, {SIG_IGN, [], 0}, 8) = 0
[pid 13829] rt_sigaction(SIGINT, NULL, {SIG_DFL, [], 0}, 8) = 0
[pid 13829] rt_sigaction(SIGTERM, NULL, {SIG_DFL, [], 0}, 8) = 0

So I don't think we are actually getting an IllegalArgumentException in 
this case. Maybe you are seeing something different?

-Alan.