Re: Bug in ulimit ?

[Stephane Chazelas <Stephane_Chazelas@xxxxxxxx>]

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?