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

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

[stone_wang]

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

Signed-Off-By: Stone Wang  <stone_wang@sohu.com>

diff -urpN linux-2.6.11-rc5-original/kernel/sys.c linux-2.6.11-rc5-cleanup/kernel/sys.c
--- linux-2.6.11-rc5-original/kernel/sys.c      2005-02-26 17:34:38.000000000 -0500
+++ linux-2.6.11-rc5-cleanup/kernel/sys.c       2005-02-27 17:27:20.000000000 -0500
@@ -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;

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Re: [PATCH] Linux-2.6.11-rc5: kernel/sys.c setrlimit() RLIMIT_RSS cleanup

[Andrew Morton]

<stone_wang@sohu.com> wrote:
>
> $ ulimit  -m 100000
>  bash: ulimit: max memory size: cannot modify limit: Function not implemented

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.
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Re: [PATCH] Linux-2.6.11-rc5: kernel/sys.c setrlimit() RLIMIT_RSS cleanup

[Rik van Riel]

On Sun, 27 Feb 2005 stone_wang@sohu.com wrote:

> 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. 

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
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Re: [PATCH] Linux-2.6.11-rc5: kernel/sys.c setrlimit() RLIMIT_RSS cleanup

[Peter Chubb]

>>>>> "Andrew" == Andrew Morton <akpm@osdl.org> writes:

Andrew> <stone_wang@sohu.com> wrote:
>>  $ ulimit -m 100000 bash: ulimit: max memory size: cannot modify
>> limit: Function not implemented

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*
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