Linux-2.6.11-rc5: kernel/sys.c setrlimit() RLIMIT_RSS cleanup

ulimit dont enforce RLIMIT_RSS now,while sys_setrlimit() pretend it(RLIMIT_RSS) is enforced.

This may cause confusion to users, and may lead to un-guaranteed dependence on "ulimit -m" to limit users/applications.

The patch fixed the problem.

-- snip from system run with patched(patch attached) 2.6.11-rc5 kernel

$ ulimit  -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
file size               (blocks, -f) unlimited
pending signals                 (-i) 1024
max locked memory       (kbytes, -l) 32
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 4091
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

$ ulimit  -m 100000
bash: ulimit: max memory size: cannot modify limit: Function not implemented

-
patch: 2.6.11-rc5 kernel/sys.c setrlimit() RLIMIT_RSS cleanup

diff -urpN linux-2.6.11-rc5-original/kernel/sys.c linux-2.6.11-rc5-cleanup/kernel/sys.c
@@ -1488,6 +1488,14 @@ asmlinkage long sys_setrlimit(unsigned i
        if (new_rlim.rlim_cur > new_rlim.rlim_max)
                return -EINVAL;
        old_rlim = current->signal->rlim + resource;
+
+       /* We dont enforce RLIMIT_RSS ulimit yet. But for application
+          compatability, we warn only when asked to change system default value. */
+       if( resource == RLIMIT_RSS &&
+           ((new_rlim.rlim_max != old_rlim->rlim_max)||
+            (new_rlim.rlim_cur != old_rlim->rlim_cur)) )
+               return -ENOSYS;
+
        if ((new_rlim.rlim_max > old_rlim->rlim_max) &&
            !capable(CAP_SYS_RESOURCE))
                return -EPERM;

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to [email protected]. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"[email protected]"> [email protected] </a>

I don't know about this. The change could cause existing applications and scripts to fail. Sure, we'll do that sometimes but this doesn't seem important enough.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to [email protected]. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"[email protected]"> [email protected] </a>

Andrew> I don't know about this. The change could cause existing Andrew> applications and scripts to fail. Sure, we'll do that Andrew> sometimes but this doesn't seem important enough.

What's more, there have been (and still are) out-of-tree patches to enforce rlimit-RSS in various ways. There just hasn't been consensus yet on the best implementation.

Dr Peter Chubb  http://www.gelato.unsw.edu.au  peterc AT gelato.unsw.edu.au
The technical we do immediately,  the political takes *forever*
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to [email protected].  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"[email protected]"> [email protected] </a>

Some kernels do enforce the RSS rlimit. Your patch could break systems that have the RSS rlimit in their configuration files because they used to run a kernel that enforces the RSS rlimit.

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it." - Brian W. Kernighan
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to [email protected].  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"[email protected]"> [email protected] </a>