Re: [tip:perf/urgent] x86: Ignore trap bits on single step exceptions

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On Thu, Nov 18, 2010 at 09:23:09AM -0600, Jason Wessel wrote:
> On 11/18/2010 08:04 AM, tip-bot for Frederic Weisbecker wrote:
> > Commit-ID:  6c0aca288e726405b01dacb12cac556454d34b2a
> > Gitweb:     http://git.kernel.org/tip/6c0aca288e726405b01dacb12cac556454d34b2a
> > Author:     Frederic Weisbecker <fweisbec@xxxxxxxxx>
> > AuthorDate: Thu, 11 Nov 2010 21:18:43 +0100
> > Committer:  Frederic Weisbecker <fweisbec@xxxxxxxxx>
> > CommitDate: Fri, 12 Nov 2010 14:51:01 +0100
> >
> > x86: Ignore trap bits on single step exceptions
> >
> > When a single step exception fires, the trap bits, used to
> > signal hardware breakpoints, are in a random state.
> >
> > These trap bits might be set if another exception will follow,
> > like a breakpoint in the next instruction, or a watchpoint in the
> > previous one. Or there can be any junk there.
> >
> > So if we handle these trap bits during the single step exception,
> > we are going to handle an exception twice, or we are going to
> > handle junk.
> >
> > Just ignore them in this case.
> >
> > This fixes https://bugzilla.kernel.org/show_bug.cgi?id=21332
> >
> > Reported-by: Michael Stefaniuc <mstefani@xxxxxxxxxx>
> > Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> > Cc: Rafael J. Wysocki <rjw@xxxxxxx>
> > Cc: Maciej Rutecki <maciej.rutecki@xxxxxxxxx>
> > Cc: Alexandre Julliard <julliard@xxxxxxxxxx>
> > Cc: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
> >   
> 
> Thankfully no more new kgdb regressions here :-)
> 
> Tested-by: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
> 
> Thanks,
> Jason.


Hehe :)

Yeah it did successfully pass the kgdb regression tests!

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