Re: [PATCH 1.5/2] generic-smp: fix initial quiesent count.

Peter Zijlstra
2009-02-14T21:17:23Z

On Sat, 2009-02-14 at 15:46 +0100, Peter Zijlstra wrote:
> first compile, then send out...
>
> ---
> Subject: generic-smp: fix initial quiesent count.
> From: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Date: Sat Feb 14 15:36:07 CET 2009
>
> If we start with a quiesent sequence count of 0, we'll match the initial stamp
> values of the cfd_data, and never make any progress.
>
> To avoid getting stuck in this situation, start out with an increased quiesent
> sequence count.

OK, so this is not going to fix the problem in generic. Its still
possible to end up with the original issue.

We'd need a callback list to free used entries, much like regular RCU,
this quiesent sequence count's wrapping just seems too brittle.