Re: the mmap() problem, a'la "grep x /dev/zero"

Michael Meskes (meskes@informatik.rwth-aachen.de)
Thu, 6 Jun 1996 14:26:21 +0200 (MET DST)

Linus Torvalds writes:
> I suspect it's just the fact that Linux doesn't check for memory availability
> when doing memory mappings. It _does_ check when increasing the bss, so it
> was just a matter of doing that check in both places (the check should
> probably be improved too).
>
> I'm including totally untested patches - I haven't even rebooted (or
> compiled) this kernel yet, but the more testers, the merrier. The worst
> that can happen is that nothing works, it eats your harddisk, and the
> machine goes up in smoke.,.
>
> (most of this patch is actually just moving "sys_brk()" to where it
> belongs)
>
> Please do tell if this makes a difference for you..

For me there's no different bahaviour at all. I killed the grep when it was
clearly over the limit I set.

But for the following program there was a change:

#include <stdio.h>
#define K 1024
#define M (1020*K)
#define N 128
char a[N*M];

main()
{
long i;

for(i=0;i<(N*M);i++)
a[i]=i%100;
}

Instead of killing my machine it dumps core. Not exactly what it should do
but better than killing the system :-)

BTW this program is the one my collegue uses to kill my machine from time to
time.

Michael

-- 
Michael Meskes                   |    _____ ________ __  ____
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