linux-kernel - Re: [PATCH tip/core/rcu 0/6] rcu: fix synchronize_rcu

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Message-ID: <20091014202853.GD2395@feather>
Date:	Wed, 14 Oct 2009 13:28:53 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, dvhltc@...ibm.com, niv@...ibm.com,
	tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
	Valdis.Kletnieks@...edu, dhowells@...hat.com, npiggin@...e.de,
	jens.axboe@...cle.com
Subject: Re: [PATCH tip/core/rcu 0/6] rcu: fix synchronize_rcu_expedited(),
 update docs, improve perf

On Wed, Oct 14, 2009 at 10:15:17AM -0700, Paul E. McKenney 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).
> 
> o	Fix to the severe performance problem with excessive IPIs and
> 	lock contention in presence of very large (but legal) numbers
> 	of RCU callbacks (reported by Nick Piggin).
> 
> o	Stopgap fix for a bug in TREE_PREEMPT_RCU's implementation of
> 	synchronize_rcu_expedited().  This fix is correct, but no faster
> 	than synchronize_rcu().
> 
> o	Add exports for the updated synchronize_rcu_expedited()
> 	implementation, which moved from a static inline in
> 	include/linux/rcupdate.h to a separately compiled function
> 	in kernel/rcutree_plugin.h.
> 
> 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 believe that this is 2.6.32 material.
> 
>  Documentation/RCU/trace.txt   |   22 ++-
>  b/Documentation/RCU/trace.txt |  232 +++++-------------------------------------
>  b/include/linux/rcutree.h     |    6 -
>  b/kernel/rcutree.c            |   29 ++++-
>  b/kernel/rcutree.h            |    5 
>  b/kernel/rcutree_plugin.h     |   20 +++
>  b/kernel/rcutree_trace.c      |    8 -
>  kernel/rcutree_plugin.h       |    3 
>  8 files changed, 103 insertions(+), 222 deletions(-)

For all of these patches except 5/6 (commented on separately):
Acked-by: Josh Triplett <josh@...htriplett.org>

I agree that these need to go into 2.6.32, to accompany the switch to
using hierarchical RCU exclusively.

- Josh Triplett
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