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SubjectRe: gdb strangness Under 2.3.11-pre1

On Tue, 13 Jul 1999, Jeremy Katz wrote:

> Doing some development and using gdb to try to debug seems to be causing
> some sort of kernel problem under 2.3.11-pre1. When tracing a running
> process, I get to the point where attempting to execute any command yields
> the following.
> Trace/breakpoint trap (core dumped)

yes this bug was introduced by the 'many threads' changes in pre-2.3.11.
The changes are a rather massive rewrite all across x86-land [we got rid
of the one-TSS-one-thread limitation] - i tried to fix all bugs, but i
think this gdb thing remained unfixed. My best guess right now is that
%db7 is being handled incorrectly somehow - although i cannot see how.

other things that might pop up:

- possible LDT related bugs - Wine people please watch out.
- ptrace/strace related bugs
- possible vm86 related bugs - i tested this rather extensively
though.

[there is another x86 change that went in as well recently with
pre-2.3.11, the 'lazy TLB flush feature' which was planned for quite some
time already - bug the gdb bug predates the lazy-TLB-flush changes. The
lazy-TLB feature lets us cut down on the number of TLB flushes rather
heavily, in a typical x86 Linux box about 80-90% of TLB flushes are now
gone.]

-- mingo


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