Re: Bug in ulimit ?

[David Peer <davidpeer@xxxxxxxxxxxxx>]

I hope kernel people will add it to the next kernel release,

but here is one rapid fix that solves the problem.

(you will not see the new limit of 1 sec but you'll still see it set to 
0, but its 1 sec - believe me && try,

if you want to see it, fork another any shell and you'll see it....bug 
or feature?!)


Before the line: *old_rlim = new_rlim;


add:


if (resource == RLIMIT_CPU && new_rlim.rlim_cur == 0) {
           /*
            * The caller is asking for an immediate RLIMIT_CPU
            * expiry.  But we use the zero value to mean "it was
            * never set".  So let's cheat and make it one second
            * instead
            */
           new_rlim.rlim_cur = 1;
       }


You can remove the dumb if statement that does nothing cause the 
assignment occurs(*old_rlim = new_rlim) before

so it has no meaning! : if (rlim_cur == 0) {....}


David



Stephane Chazelas wrote:

> On Tue, Apr 17, 2007 at 02:24:46PM +0100, Stephane Chazelas wrote:
>   
> > On Tue, Apr 17, 2007 at 02:03:16PM +0100, Stephane Chazelas wrote:
> > [...]
> >     
> > > So it would seem that the limit is inherited but not applied in
> > > the child (and I couldn't see any signal being blocked or
> > > ignored). So that's probably not a libc issue, rather a Linux
> > > issue.
> > >       
> > [...]
> >     
>
> Please ignore this email, I was talking rubbish again, I should
> probably get back to sleep....
>
>   
> > The Linux code for setrlimit gives a hint:
> >
> >         if (it_prof_secs == 0 || new_rlim.rlim_cur <= it_prof_secs) {
> >                 unsigned long rlim_cur = new_rlim.rlim_cur;
> >                 cputime_t cputime;
> >
> >                 if (rlim_cur == 0) {
> >                         /*
> >                          * The caller is asking for an immediate RLIMIT_CPU
> >                          * expiry.  But we use the zero value to mean "it was
> >                          * never set".  So let's cheat and make it one second
> >                          * instead
> >                          */
> >                         rlim_cur = 1;
> >                 }
> >
> > It's stored as being "0" and armed with a 1 second delay. And on a fork,
> > obviously, for the new process, there's no way to distinguish
> > between a 0 that means "not set" and a 0 that means exit
> > immediately.
> >
> > And one can verify that it_prof_expires will be set to 0 in
> > copy_signal during the fork and that 0 means not armed in
> > check_process_timers.
> >
> > But what's the point of setting a cputime of 0 anyway?
> >     
>
>   


--
David Peer <!> davidpeer@xxxxxxxxxxxxx
CS System Group | Phone: 02 - 6586942
School of Computer Science and Engineering
Hebrew University of Jerusalem - Israel
Edmund Safra Campus - Givat Ram