On 04.04.13 20:47, Richard Tew wrote:
On Fri, Apr 5, 2013 at 4:09 AM, Kristján Valur Jónsson
<[email protected] <mailto:[email protected]>> wrote:
I’ve been thinking some more about this.
It should be ok to kill a tasklet that hasn’t run yet. And
killing a dead one should be a no-op.
Rather than making “kill” have special semantics, how about just
applying that rule? An exception sent to a tasklet that hasn´t
run yet just disappears and the tasklet dies.
An exception sent to a dead tasklet just disappears.
I think these are sensible semantics. In my opinion, it was a
mistake to design stackless such that uncought tasklet exceptions
were sent to the main tasklet.
I disagree. I think there's an argument to be made that when a new
tasklet gets inserted into the scheduler, it is effectively running.
The user does not know, or care, when it actually starts running as
long as it duly gets run in a fair manner. My expectation would be
that an exception raised on a not yet run by (but inserted in) the
scheduler tasklet, would be raised on the main tasklet - as it has not
been caught. Also, I would expect that raising an exception on a dead
tasklet would error.
For the most part, I just start tasklets. I expect them to run. But
when I start micromanaging them and holding references to them to do
more advanced usage, I already do things like checking to see if they
are alive before performing operations on them. Or checking to see
if they are blocked on a channel. Or whatever. I think that based on
my usage of tasklets, if someone is throwing exceptions on tasklets,
they should be explicit in terms of the expected situation. This
means that it is not unreasonable to expect them to check the tasklets
state before raising exceptions on them.
I'm in the same boat.
Letting things just pass trough as a no-op is error-prone, because
it hides programming errors where an alive tasklet is expected,
but it was dead.
I believe it is better to support explicitly the expected situation instead
of making things too "handy", meaning sloppy style.
Fiddling around with tasklets is anyway not a feature that should
normally be used by users, so it is probably used in a framework.
But there things should be clean and unambiguous, to avoid hard to
track errors.
cheers - chris
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