linux-kernel - Re: [PATCH tip/core/rcu 0/4] RCU debug-objects improvements

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Message-ID: <20130424024849.GE3427@linux.vnet.ibm.com>
Date:	Tue, 23 Apr 2013 19:48:49 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Sedat Dilek <sedat.dilek@...il.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, josh@...htriplett.org,
	niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, Valdis.Kletnieks@...edu, dhowells@...hat.com,
	edumazet@...gle.com, darren@...art.com, fweisbec@...il.com,
	sbw@....edu, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	Rik van Riel <riel@...riel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH tip/core/rcu 0/4] RCU debug-objects improvements

On Wed, Apr 24, 2013 at 03:45:20AM +0200, Sedat Dilek wrote:
> [ QUOTE ]
> 
> Hello!
> 
> RCU's current debug-objects fixups are complex and heavyweight, plus the
> fixups are not complete, because even with the fixups, RCU's callback
> lists can still be corrupted.  This series reworks RCU's use of the
> debug-objects facility and the facility itself to allow improved handling
> of things like duplicate invocations of call_rcu().  This series includes:
> 
> 1.	Simplify RCU's debug-objects fixups.
> 
> 2.	Make debug_object_activate() return status.
> 
> 3.	Make __call_rcu() leak callbacks when debug_object_activate()
> 	notes suspicious activity.  Leaking has its problems, but it
> 	is far better than silent corruption of RCU's data structures.
> 
> 4.	Add a new object_debug option to rcutorture to allow
> 	deterministic testing of #3 above.
> 
> 							Thanx, Paul
> 
> 
>  b/include/linux/debugobjects.h |    6 +-
>  b/kernel/rcu.h                 |   10 ++--
>  b/kernel/rcupdate.c            |  100 -----------------------------------------
>  b/kernel/rcutorture.c          |   37 +++++++++++++++
>  b/kernel/rcutree.c             |   14 +++++
>  b/lib/debugobjects.c           |   20 +++++---
>  6 files changed, 74 insertions(+), 113 deletions(-)
> 
> [ /QUOTE ]
> 
> I applied your patchset against the "buggy" Linux-Next (next-20130423)
> with none of the ipc-sem-next patches (even w/o the suggested Linus
> patch) to see if I see more debug-outputs,
> 
> I have attached my syslog while building my kernel.
> Please, have a look!

The warnings and the leaking of the offending callback are all present,
thank you for testing this!

> Thanks for the patches.
> 
> Feel free to add to all of the 4 patches my Tested-by.

Will do!

						Thanx, Paul

> - Sedat -
> 
> [1] http://marc.info/?l=linux-kernel&m=136676361101735&w=2



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