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

Ingo Molnar
2009-10-15T11:21:13Z

* 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.

Ingo