Re: zsh-2.6beta20 doesn't compile under Linux pre2.0.14

[Steven L Baur <steve@xxxxxxxxxxxx>]

>>>>> "Zoltan" == Zoltan Hidvegi <hzoli@xxxxxxxxxx> writes:

(Your patch produces a compilable zsh on Linux 2.0, thanks).

Zoltan> It is surprising that the there days before the final 2.0
Zoltan> release a new feature appeared.  Here is the patch.  I think
Zoltan> zsh will be the first shell which can set this new limit.
Zoltan> There is no patch to the manual simply because I do not know
Zoltan> what is this limit.  Also a new flag should be inveted to set
Zoltan> this limit with ulimit.

It's related to the problem found recently where ``grep x /dev/zero''
would crash the system.  I don't believe it does anything, at least I
haven't found any code via grep in the kernel source that does
anything with it.

Zoltan> Please tell me your suggestions.

Here's the only authoritative information about it I'm aware of:
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Date: 	Fri, 7 Jun 1996 09:22:26 +0300 (EET DST)
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxx>
To: Michael Meskes <meskes@xxxxxxxxxxxxxxxxxxxxxxxxx>
cc: Linux-Kernel Mailinglist <linux-kernel@xxxxxxxxxxxxxxxx>
Subject: Re: the mmap() problem, a'la "grep x /dev/zero"
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On Fri, 7 Jun 1996, Michael Meskes wrote:
> 
> circe:meskes 105) grep x /dev/zero
> grep: memory exhausted

Umm, this looks ok - that's what supposed to happen. Linux can't fix the 
fact that grep doesn't work well on /dev/null (or any file that is that 
huge), but at least the above isn't a crash..

> It allocated much more memory than it should. I had a limit of 4MB, but the
> size went up to 12MB (5MB resident).

Umm, _what_ size? If you set a RLIMIT_DATA (or whatever the name is), 
that will only make a difference for the process bss (*), and if grep 
uses mmap(), then we'd need to have a "virtual memory" limit. However, we 
don't have any such limit, although I added a RLIMIT_AS for 2.0 (but it's 
currently unchecked).

(*) that's the curent Linux interpretation, at least. Do other unixes 
consider mmap'ed data part of RLIMIT_DATA?

>	 			Also I was able to run the memtest
> program on 8MB despite datasize limited to 1MB. Hmm I have to check the
> sources to see what happened. And my program with a global definition of
> 'char a[128MB]' still dumpos core.

Well, dumping core is the corect thing to do - it failed to get the BSS 
at exec time, so when the program actually ran it was "kind of" unhappy..

		Linus


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