[uml-devel] [Sebastian.Koch@metatool.de: Re: ps u failed with signal 8 (FPE)]

[uml-devel] [Sebastian.Koch@metatool.de: Re: ps u failed with signal 8 (FPE)]

[Gerd Knorr]

  Hi,

"ps u" doesn't work in uml due to some values in /proc/meminfo being zero,
see below for details,

  Gerd

----- Forwarded message from Sebastian Koch <Sebastian.Koch@metatool.de> -----

Date: Thu, 22 Jan 2004 11:20:17 +0100 (MET)
From: Sebastian Koch <Sebastian.Koch@metatool.de>
Subject: Re: ps u failed with signal 8 (FPE)
To: Albert Cahalan <albert@users.sf.net>
cc: Sebastian Koch <Sebastian.Koch@metatool.de>,
   Gerd Knorr <kraxel@bytesex.org>
Importance: high
Content-Type: TEXT/PLAIN; charset=US-ASCII
X-Bogosity: Unsure, tests=bogofilter, spamicity=0.482720, version=0.15.13

I've found it.

The problem is that the proc file system of the UML shows a wrong
/proc/meminfo. Especially the MemTotal:

Achen:~ # p /proc/meminfo
MemTotal:            0 kB
MemFree:         33656 kB
Buffers:           752 kB
Cached:          19756 kB
SwapCached:          0 kB
Active:          12236 kB
Inactive:        10600 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:            0 kB
LowFree:         33656 kB
SwapTotal:      262136 kB
SwapFree:       262136 kB
Dirty:              16 kB
Writeback:           0 kB
Mapped:           5360 kB
Slab:             3264 kB
Committed_AS:    27144 kB
PageTables:        172 kB
VmallocTotal:   449516 kB
VmallocUsed:       184 kB
VmallocChunk:   449332 kB
Achen:~ #

This leeds to divide by zero in ps/output.c line 785 because the
kb_main_total == 0.


/* pp->vm_rss * 1000 would overflow on 32-bit systems with 64 GB memory */
static int pr_pmem(char *restrict const outbuf, const proc_t *restrict
const pp){
  unsigned long pmem = 0;
  pmem = pp->vm_rss * 1000ULL / kb_main_total;
  if (pmem > 999) pmem = 999;
  return snprintf(outbuf, COLWID, "%2u.%u", (unsigned)(pmem/10),
(unsigned)(pmem%10));
}

Do you want to setup a consistence check after reading the proc/meminfo ?

I will try to find out the problem in UML.

Best regards
Sebastian



On 20 Jan 2004, Albert Cahalan wrote:

> On Tue, 2004-01-20 at 10:46, Sebastian Koch wrote:
>
> > Probably this is a known bug.
>
> Nope. I've not seen this one.
>
> > If you need additional information regarding the UML-, host-kernel or
> > the root file system please let me know. I can provide a backtrace if someone
> > point me out where to set a breakpoint. To be honest I don't understand the
> > kernel FPE signal handling at this moment.
>
> This could be caused by integer division by zero.
> If you can get the siginfo data, that would be
> enough to determine this.
>
> Also, try this:   ps --info
>
>
>

--



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Re: [uml-devel] [Sebastian.Koch@metatool.de: Re: ps u failed with signal 8 (FPE)]

[Goetz Bock]

On Thu, Jan 22 '04 at 12:48, Gerd Knorr wrote:
> "ps u" doesn't work in uml due to some values in /proc/meminfo being zero,
> see below for details,
Works fine here:

user@uml ~$ ps u
USER      PID %CPU %MEM   VSZ  RSS TTY      STAT START   TIME COMMAND
user     7112  0.0  0.0  2200    4 pts/1    S    Jan03   0:00 /bin/bash
user    12177  0.0  1.5  2192  444 pts/0    S    Jan09   0:00 -bash
user    12182  0.0  1.8  2312  520 pts/0    S    Jan09   0:00 screen -r
user    12219  0.0  4.6  2208 1288 pts/2    S    Jan09   0:00 /bin/bash
user    12224  0.0  2.5  2536  724 pts/2    R    Jan09   0:00 ps u
user@uml ~$ cat /proc/meminfo
        total:    used:    free:  shared: buffers:  cached:
 Mem:  28614656 27774976   839680        0   806912 21946368
Swap: 134209536 11239424 122970112
MemTotal:        27944 kB
MemFree:           820 kB
MemShared:           0 kB
Buffers:           788 kB
Cached:          20028 kB
SwapCached:       1404 kB
Active:           1968 kB
Inactive:        21180 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:        27944 kB
LowFree:           820 kB
SwapTotal:      131064 kB
SwapFree:       120088 kB
user@uml ~$ cat /proc/version
Linux version 2.4.22-4bgstatic-6um (root@basel1.hfz.info) (gcc version 3.3) #1 Mon Dec 1 01:18:56 CET 2003

user@host ~$ cat /proc/version
Linux version 2.4.23-0tr1bg (root@basel1.hfz.info) (gcc version 3.3) #1 Sun Nov 30 17:08:50 CET 2003


So what version of uml are you talking about.
-- 
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\ /                     (c) 2003 as GNU FDL 1.1
 X   [ 1. Use descriptive subjects - 2. Edit a reply for brevity -  ]
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[uml-devel] Re: [Sebastian.Koch@metatool.de: Re: ps u failed with signal 8 (FPE)]

[Gerd Knorr]

Goetz Bock <bock+uml@blacknet.de> writes:

> On Thu, Jan 22 '04 at 12:48, Gerd Knorr wrote:
> > "ps u" doesn't work in uml due to some values in /proc/meminfo being zero,
> > see below for details,
> Works fine here:

> user@uml ~$ cat /proc/version
> Linux version 2.4.22-4bgstatic-6um (root@basel1.hfz.info) (gcc version 3.3) #1 Mon Dec 1 01:18:56 CET 2003

The kernel in question is 2.6.x ...

  Gerd

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Re: [uml-devel] [Sebastian.Koch@metatool.de: Re: ps u failed with signal 8 (FPE)]

[Jeff Dike]

kraxel@bytesex.org said:
> The problem is that the proc file system of the UML shows a wrong /
> proc/meminfo. Especially the MemTotal: 

Nice catch.  I was wondering about that SIGFPE crash.  Try the patch below.

				Jeff

===== arch/um/kernel/mem.c 1.21 vs edited =====
--- 1.21/arch/um/kernel/mem.c   Thu Jan  8 07:43:01 2004
+++ edited/arch/um/kernel/mem.c Mon Jan 26 11:02:13 2004
@@ -30,7 +30,6 @@
 int kmalloc_ok = 0;
 
 static unsigned long brk_end;
-static unsigned long totalram_pages = 0;
 
 void unmap_physmem(void)
 {



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