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Subject: Re: Core dumps for threads
To: n0ano@valinux.com (Don Dugger)
Date: Sat, 24 Feb 2001 21:57:44 +0000 (GMT)
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <20010224134523.O26109@valinux.com> from "Don Dugger" at Feb 24, 2001 01:45:23 PM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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> Can anyone explain why this test is in routine `do_coredump'
> in file `fs/exec.c' in the 2.4.0 kernel?
> 
>     if (!current->dumpable || atomic_read(&current->mm->mm_users) != 1)
> 	goto fail;
> 
> The only thing the test on `mm_users' seems to be doing is stopping
> a thread process from dumping core.  What's the rationale for this?

The I/O to dump the core would race other changes on the mm. The right fix
is probably to copy the mm (as fork does) then dump the copy.

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