Re: [RFA]: Modified Watchthreads Patch

[Mark Kettenis <kettenis at gnu dot org>]

   Date: Fri, 10 Dec 2004 18:52:37 -0500
   From: Jeff Johnston <jjohnstn@redhat.com>

   As I observed before, the actual watchpoint only needs to be set on
   one thread and it will trigger in other threads.  I can send you
   the additional patch if you want to experiment with it.

This is highly suspicious.  I think it means that there is a bug in
the kernel.  Of course that's in the eye of the beholder since the
there is no documentation whatsoever how watchpoints should work in
the Linux kernel.  I think that, before we change GDB, we should
insists that this gets properly documented, and agreed on by the
kernel people.

   I am still waiting for a machine with the latest RH kernel on it.
   I'll let you know if that works the same.

What the latest RH kernel does should be mostly irrelevant to the GDB
project.  What matters is what the official Linux kernel does.  We
should realize that not everybody is using a kernel that was released
just a week ago.  GDB should also work on older kernels (we've
previously stated that it will work on version 2.0 and later).  Of
course we don't support all features on those kernels, but we
shouldn't break features that worked on those kernels before.  It
seems to me the i386 watchpoint issue has a high-risk to break older
kernels.

Mark