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Re: Race condition in Mach/Hurd?

From: Svante Signell
Subject: Re: Race condition in Mach/Hurd?
Date: Tue, 10 May 2011 12:31:16 +0200

On Mon, 2011-05-09 at 18:43 +0200, Samuel Thibault wrote:

> > Single stepping in msgserver.c also triggered the console printout: task
> > 5040ee18 deallocating an invalid port 340/xxx, most probably a bug.
> Note that you can make the kernel start the in-kernel debugger in that
> case. Simply set the mach_port_deallocate_debug variable to 1, or use nm
> on the "gnumach" binary to get its adress, e.g. 0x20001234, and use
> w 20001234 1
> cont
> from the kernel debugger (use ctrl-alt-d to invoke it) to write a 1
> there.

It's not so simple as you say: I have now found out where the
mach_port_deallocate_debug variable is in gnumach-1.3.99-486-dbg (copied
from boot and uncompressed). I have two alternatives:

1) Write a one into that address without using the kernel debugger, how?
Then I could compress it again, and put it back in /boot!

2) Uncompress it at /boot
Start the debugger with C-A-d. Does this work on an uncompressed image?
w 002c10c0 1
and then, how to exit the debugger?
Then compress the image again, and restarting the debugger??

When should I start the kernel debuggger, before or after triggering:
5040ee18 deallocating an invalid port 340, most probably a bug.

Is there any help available for the kernel debugger?

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