Re: [patch 1/2] x86_64 page fault NMI-safe

From: Peter Zijlstra
Date: Fri Aug 06 2010 - 05:52:22 EST

On Thu, 2010-08-05 at 21:49 -0400, Mathieu Desnoyers wrote:
> * Peter Zijlstra (peterz@xxxxxxxxxxxxx) wrote:
> > On Wed, 2010-08-04 at 10:45 -0400, Mathieu Desnoyers wrote:
> >
> > > How do you plan to read the data concurrently with the writer overwriting the
> > > data while you are reading it without corruption ?
> >
> > I don't consider reading while writing (in overwrite mode) a valid case.
> >
> > If you want to use overwrite, stop the writer before reading it.
> How inconvenient. It happens that the relatively large group of users I am
> working for do care for this use-case. They cannot afford to stop tracing as
> soon as they hit "one bug". This "bug" could be a simple odd scenario that they
> want to snapshot, but in all cases they want tracing to continue.

Snapshot is fine, just swivel the whole buffer.
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