Review request for 6829503

[Alan Bateman]

David Holmes - Sun Microsystems wrote:
> :
> But a runtime exception is better than silent failure when the file 
> will not be deleted. And the exception here is not new.
>
> Is this a flaw in the File#deleteOnExit API - because it gives the 
> illusion that it can always succeed when in fact the code requesting 
> this can be running concurrently with the code responsible for making 
> it happen? Maybe that is a deficiency of the whole mechanism - really 
> we should be using a native deletion mechanism that is only done once 
> the VM arrives at the termination safepoint - as that is the only time 
> we know for sure that no more Java code can be executed. But that 
> would be a RFE on the deleteOnExit mechanism.
I agree that a runtime exception is better than silently not registering 
but it really needs to be specified or as you suggest, delete the files 
once we have reached the termination safepoint. As creating a file and 
registering it for delete via deleteOnExit is not an atomic operation 
then there will always be a window where the VM may exit before the 
application registers the delete. An IllegalStateException gives some 
opportunity to explicitly delete the file but there is no guarantee that 
such a recovery action will execute. It is somewhat helpful in that it 
may prevent code from writing sensitive information to a file that it 
expects to be deleted.

Anyway, the history is that this mechanism used to be completely in 
native code and the files deleted via a VM exit hook. I haven't looked 
at this code in a while but my memory is that these exit hooks are 
executed by before_exit after the shutdown hooks but before the 
cancellation safepoint. The IllegalStateException came with the re-write 
in jdk6 to keep the list in the java heap to make it easier to diagnose 
resource issues caused by applications that registered tens of thousands 
of files to be deleted. At that point the spec should have been looked 
at. As it happens, there was a bug in that code (6526376) that caused 
NPE to be thrown so jdk7 b10 is the first build where 
IllegalStateException is possible.

I don't think we want to force Mandy into fixing issues that aren't of 
her doing so submitting a bug and letting her move on is probably the 
best thing to do.

-Alan.