Re: [PATCH] xargs with large (or zero) max-procs

[James Youngman]

On Dec 26, 2007 10:51 PM, Marc Aurele La France <address@hidden> wrote:
> Hi.
>
> The -p1 patch below causes `xargs` to reap its zombied children before
> attempting to fork() another child process.  This is intended to make it
> more difficult for a user to fill up the process table, potentially
> causing other system services to fail.

First thanks for reporting the bug.   I have recorded it at
http://savannah.gnu.org/bugs/index.php?21960

I opted for a fix that is somewhat different to your proposal.  I
wanted to have xargs reap children a little more frequently than
provided for in your code change (for example, before fork when -P50
is in effect).   Also though, xargs had a number of variables which
were signed but not indended to hold a negative quantity; some of
these related to counting the number of outstanding child processes.
I took the opportunity to fix that too.

The change I prepared was emailed (as usual) to
address@hidden and is attached to the bug at the above URL.
 I'll apply it to the CVS tree in a couple of days, once people have
had an opportunity to review it.

This means that despite your work to fix this problem, the code change
you suggested wasn't the one I used.   I hope you don't mind.
Nevertheless your change was a good one and should you want to further
contribute to findutils, we'd be glad of the help.

> This is keyed on whether or not <sys/wait.h> #define's WNOHANG, but you
> might want to key off of the existence of waitpid(), using the automangle
> suite.  I am submitting this in its current form given that waitpid() is
> just about as old as wait(), older than wait3() and wait4() even, and that
> there is no point in WNOHANG without waitpid() or vice-versa.

I agree that waitpid is well-established.   Every bit of
autoconfiscation imposes a small extra maintenance burden.   Partly
for that reason, I decided to just assume the existence of both
waitpid() and WNOHANG.

Thanks again for your help.

James.