Re: [PATCH tip/core/rcu 0/6] rcu: fix synchronize_rcu_expedited(), update docs, improve perf

Paul E. McKenney
2009-10-15T18:41:23Z

On Thu, Oct 15, 2009 at 01:19:44PM +0200, Ingo Molnar wrote:
>
> * Josh Triplett <josh@joshtriplett.org> wrote:
>
> > On Thu, Oct 15, 2009 at 11:21:55AM +0200, Ingo Molnar wrote:
> > > * Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
> > >
> > > > This patchset contains a bug fix, a performance improvement, and
> > > > documentation updates:
> > > >
> > > > o Update Documentation/RCU/trace.txt to reflect recent changes
> > > > (including the removal of rcupreempt.c).
> > >
> > > i've applied this to the .33 queue.
> >
> > I realize this only represents a documentation change, but it updates
> > the documentation to match the code in 2.6.32, which seems worth
> > doing.
> >
> > > > o Add the new rnp->blocked_tasks field to the rcuhier trace file
> > > > in debugfs.
> > > >
> > > > o Update the Documentation/RCU/trace.txt documentation to include
> > > > the rnp->blocked_tasks tracing.
> > >
> > > i've applied these to the .33 queue as well. (both tracing and
> > > documentation is not urgent material.) I also did minor edits to the
> > > changelogs.
> >
> > Those who debug RCU-related issues would disagree that having adequate
> > tracing information proves non-urgent. :) The tracing information this
> > adds proves essential for debugging issues with the new hierarchical
> > RCU. (And the documentation patch just documents the added tracing
> > information, so both should go together as a unit; actually, perhaps
> > they should get merged.)
>
> No, we generally dont do such changes so late in -rc's (these would hit
> upstream in -rc6 - which is too late).
>
> People doing development will use the latest RCU tree so the practical
> impact is small. Furthermore, we had a higher than usual rate of
> post-rc1 RCU changes in this cycle already, it needs to cool down a bit.

Works for me! I can supply appropriate diffs off of one of the -rc
releases if people need this in order to experiment with recent RCU
patches. (But I get to choose the -rc!)

Thanx, Paul