Re: Bug in ulimit ?

[Stephane Chazelas <Stephane_Chazelas@xxxxxxxx>]

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.
[...]

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?

-- 
Stéphane