mutex-bug in recent releng_[67]?

Arno J. Klaassen arno at
Sat Nov 17 17:48:17 PST 2007

Nate Williams <nate at> writes:

> > I have serious problems with " Runtime.getRuntime ().exec ()" : either
> > it hangs or gives a spinning mutex running at 99% cpu.
> This is a Java FAQ,

Oops. Sorry for the noise ....

> and is unrelated to FreeBSD.  This program will hang
> on any OS once you reach a certain threshold of unread output that the
> OS will block the process until something 'reads' the data.
> What you need to do is once you execute the command, you need to have a
> process that reads the output from the process.

OK. I see (and most often do); but indeed I didn't in cases where I were just
interested in the exit value of the command (and then afterwards
read "proc.getErrorStream" to see what went wrong ... ).

Thank you very much for your help.

> [ .. ]
> Here is my (trivial) implementation, use it as you see fit.
> [ .. ]

Thanx! I'l try.
> Why it works on linux-sun-jdk15 is probably due to the fact that there
> is more stack space allocated to processes, but if you modified the
> process to generate more output ('ls -R /'), it will eventually fail.

Yop, you're right.


Arno (a bit ashamed)

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