Problems persist in KQueueSelectorProvider (Mac) in 7u6 ea

[Alan Bateman]

On 13/08/2012 15:06, David M. Lloyd wrote:
> :
> We did test on 6 with similar results.
>
> We've tested on the u6 tip as well as on previous 7 versions (we 
> explicitly choose the selector provider), with similar results.
Thanks for checking, at least this shows that we aren't dealing with 
something new.

> :
>
> It is definitely hanging in dup2(), as dup2() is the only thing that 
> preClose0 actually does.  As I said I implemented a test to use 
> shutdown() instead of dup2() for preClose0 but that just moved the 
> problem to the real close().
One thing that would be useful is a thread dump. A stack trace with the 
kernel frames would be useful too but may not be possible with 
stackshot, maybe need to come up with a dtrace script. At least with the 
fifo case, where we have also observed close or dup2 to hang, the issue 
is that it blocks waiting for an I/O on the fifo to complete.


>
> I suspect that while both problems are related to kqueue bugs, the 
> spin is specifically related to how setInterest works, whereas the 
> dup2 hang/stuck process is something separate.
They may be related too. In particular if dup2 has caused the file 
descriptor to reference the pre-close socket then it maye cause any 
Selector that it is registered with to spin until the key has been canceled.

-Alan.