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Date:      Sun, 18 Mar 2001 10:23:46 -0500 (EST)
From:      Andrew Gallatin <gallatin@cs.duke.edu>
To:        Doug Rabson <dfr@nlsystems.com>
Cc:        <freebsd-alpha@FreeBSD.ORG>, <jhb@FreeBSD.ORG>
Subject:   Re: user process faulting on kernel address
Message-ID:  <15028.54018.584762.460700@grasshopper.cs.duke.edu>
In-Reply-To: <Pine.BSF.4.33.0103181132120.86872-100000@herring.nlsystems.com>
References:  <15026.37378.477855.889651@grasshopper.cs.duke.edu> <Pine.BSF.4.33.0103181132120.86872-100000@herring.nlsystems.com>

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Doug Rabson writes:
 > On Fri, 16 Mar 2001, Andrew Gallatin wrote:
 > 
 > >
 > > When running a linuxthreads app which basically sits in a loop
 > > doing a pthread_create()/pthread_join() of a thread which just
 > > exits, I'll occasionally see a very interesting thing --
 > > the app dies on an instruction fault on a kernel address.
 > 
 > Could you put up a binary (static linked if possible) so that I can have a
 > go at reproducing the problem? Thanks in advance...

http://www.cs.duke.edu/~gallatin/ex6.gz

Enable the debugging printfs in trap.c.  You'll notice that it gets
"stuck" in the kernel because it SEGV's just as soon as switches back
to user mode.  It is the parent which is faulting, not a child.

I tried duplicating it with a native program that vfork()s and
wait()s, but I had no success.  I'm inclined to think it has something
to do with signal delivery.

Drew

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