Re: Bug in ulimit ?

[David Peer <davidpeer@cs.huji.ac.il>]

Thanks Tom for quick, fast fix and for sending me and others the kernel
patch.
Lets hope kernel developers will apply it in the next release, although
they know about it since 2.6.17.

Thanks!
David

On Tue, April 17, 2007 5:15 pm, Tom Alsberg wrote:
> I checked the problem earlier today (by reference of David who pointed
> it out to me - thanks, David).  The problem is apparently in the Linux
> kernel, where the check for trying to set RLIMIT_CPU = 0 is done a bit too
> late, and has nothing to do with zsh.  Specifically, the same symptoms
> were visible with other shells (ash, bash) too.
>
> I checked the Linux kernel sources and found the solution in
> kernel/sys.c.  Attached is a copy of my message with the patch to the
> Linux-Kernel Mailing List.
>
>
> One issue that may be relevant within zsh, though, is that it appears
> that zsh caches the limits set, and since that check in Linux "cheats" by
> setting the value to 1 when 0 is requested, entering "ulimit -a" does not
> call getrlimit(...) at all and does show 0 after issuing the command
> "ulimit -t 0", although getrlimit(RLIMIT_CPU, ...) would
> return 1.  The correct limit is seen in a subshell where this is not yet
> cached.
>
> I expect my patch to be in the next Linux 2.6.21 release candidate.
>
>
> Cheers,
> -- Tom
>
>
> On Tue, Apr 17, 2007 at 02:30:40AM -0700, Micah Cowan wrote:
>
>> David Peer wrote:
>>
>>> If the user run: ulimit -t 0, he can run jobs without any cputime
>>> limitation:
>>>
>>
>> This sounds more like a kernel problem to me than a zsh bug. I get the
>> same behavior on my Ubuntu 7.04 (beta) system, in _bash_.
>>
>> I note that getrlimit(2) says:
>>
>>
>> In 2.6.x kernels before 2.6.17, a RLIMIT_CPU  limit  of  0  is  wrongly
>>  treated  as "no limit" (like RLIM_INFINITY).  Since kernel 2.6.17,
>> set‐ ting a limit of 0 does have an effect, but is  actually  treated
>> as  a limit of 1 second.
>>
>> However, I'm running 2.6.20(-14-generic), and still experiencing that
>> symptom.
>
> --
> Tom Alsberg - hacker (being the best description fitting this space)
> Web page:	http://www.cs.huji.ac.il/~alsbergt/
> DISCLAIMER:  The above message does not even necessarily represent what
> my fingers have typed on the keyboard, save anything further.
>