From: Alexander Viro <viro@math.psu.edu>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Kip Macy <kmacy@netapp.com>, Elan Feingold <efeingold@mn.rr.com>,
linux-kernel@vger.kernel.org
Subject: Re: Multithreaded core dumps
Date: Thu, 30 Aug 2001 05:03:59 -0400 (EDT) [thread overview]
Message-ID: <Pine.GSO.4.21.0108300457270.9879-100000@weyl.math.psu.edu> (raw)
In-Reply-To: <E15cN7L-0000gX-00@the-village.bc.nu>
On Thu, 30 Aug 2001, Alan Cox wrote:
> > I am inclined to believe that that is the case. Unfortunately, I have no
> > advice to give - but I am writing because I think that it would be neat if
> > you have the time and the inclination for you to document your findings as
> > you progress and put them on the web.
>
> The 2.4-ac tree supports dumping core.$pid for the threads that actually
> died
... and these dumps are not reliable. Living thread may modify the
contents of dump as it's being written out. I.e. you are getting
false alarms - inconsistent data that was never there.
Think of a linked list protected by a mutex. Half of its entries are
already written out. Surviving thread removes an element. It updates
the in-core structures correctly. The problem being, in the dump
we get part of memory from before that change and part - after. If
you notice that when you are looking at the dump - welcome to a nice
chase after the bug that never existed.
next prev parent reply other threads:[~2001-08-30 9:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-08-30 5:21 Multithreaded core dumps Elan Feingold
2001-08-30 5:50 ` Kip Macy
2001-08-30 8:24 ` Alan Cox
2001-08-30 9:03 ` Alexander Viro [this message]
2001-08-30 9:12 ` Alan Cox
2001-08-30 10:08 ` Alexander Viro
2001-08-30 9:33 ` David S. Miller
2001-08-30 8:16 ` Multithreaded core dumps (CLONE_THREAD and elf) Terje Eggestad
2001-08-30 9:19 ` Andreas Dilger
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