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From: Arnd Bergmann <arnd@arndb.de>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org,
	mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com,
	akpm@linux-foundation.org, josh@joshtriplett.org,
	dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de,
	peterz@infradead.org, rostedt@goodmis.org,
	Valdis.Kletnieks@vt.edu, dhowells@redhat.com
Subject: Re: [PATCH 02/10] rcu: annotated list rcu code
Date: Wed, 24 Feb 2010 21:32:13 +0100	[thread overview]
Message-ID: <201002242132.13731.arnd@arndb.de> (raw)
In-Reply-To: <20100224201509.GB21067@Krystal>

On Wednesday 24 February 2010, Mathieu Desnoyers wrote:
> * Arnd Bergmann (arnd@arndb.de) wrote:
> > The listrcu implementation now defines new rcu_list_head,
> > rcu_hlist_head and rcu_hlist_entry structures that are
> > annotated with __rcu. Only these can now be passed into
> > rcu_list_for_each and related interfaces.
> > 
> > When not running sparse, the types are defined to the
> > original list_head etc in order to not break working
> > setups that are lacking annotation.
> 
> Hrm, wait.. dumb question: how can an annotation break compilation ? If there is
> any way out of this, I would prefer if we can do without a #ifdef __CHECKER__ if
> possible. It calls for bugs and implementation mismatch.

The problem is that you can not (currently) declare a list_head
to be RCU protected by writing 'struct list_head __rcu list;',
because address space annotations only work on pointers.

The solution I used was to define a new struct rcu_list_head that
has the ->next member annotated as __rcu. Unfortunately, this
means that it is now incompatible to a struct list_head from
the compiler's point of view.

We could get rid of the #ifdef by unconditionally defining
the separate rcu_list_head, as long as all users are correctly
converted to it. This does have problems in cases such as the
module code that uses the same list with and without RCU, as
Alexey mentioned.

The alternative would be not to annotate list RCU at all and
__force away the warnings for these so we can still keep the
normal __rcu annotations.

	Arnd


  reply	other threads:[~2010-02-24 20:38 UTC|newest]

Thread overview: 84+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-02-23  1:04 [PATCH tip/core/rcu 0/21] v6 add lockdep-based diagnostics to rcu_dereference() Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 01/21] rcu: introduce lockdep-based checking to RCU read-side primitives Paul E. McKenney
2010-02-25 10:09   ` [tip:core/rcu] rcu: Introduce " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 02/21] rcu: add lockdep-enabled variants of rcu_dereference() Paul E. McKenney
2010-02-25 10:09   ` [tip:core/rcu] rcu: Add " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 03/21] rcu: integrate rcu_dereference_check() message into lockdep Paul E. McKenney
2010-02-25 10:09   ` [tip:core/rcu] rcu: Integrate " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 04/21] rcu: disable lockdep checking in RCU list-traversal primitives Paul E. McKenney
2010-02-25 10:10   ` [tip:core/rcu] rcu: Disable " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 05/21] net: add checking to rcu_dereference() primitives Paul E. McKenney
2010-02-25 10:10   ` [tip:core/rcu] net: Add " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 06/21] sched: use lockdep-based checking on rcu_dereference() Paul E. McKenney
2010-02-25 10:11   ` [tip:core/rcu] sched: Use " tip-bot for Paul E. McKenney
2010-02-25 11:06   ` [tip:core/rcu] sched, cgroups: Fix module export tip-bot for Ingo Molnar
2010-02-23  1:04 ` [PATCH tip/core/rcu 07/21] sched: better name for for_each_domain_rd Paul E. McKenney
2010-02-25 10:11   ` [tip:core/rcu] sched: Better " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 08/21] vfs: apply lockdep-based checking to rcu_dereference() uses Paul E. McKenney
2010-02-25 10:11   ` [tip:core/rcu] vfs: Apply " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 09/21] vfs: abstract rcu_dereference_check for files-fdtable use Paul E. McKenney
2010-02-25 10:11   ` [tip:core/rcu] vfs: Abstract " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 10/21] radix-tree: disable RCU lockdep checking in radix tree Paul E. McKenney
2010-02-25 10:12   ` [tip:core/rcu] radix-tree: Disable " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 11/21] idr: apply lockdep-based diagnostics to rcu_dereference() uses Paul E. McKenney
2010-02-25 10:12   ` [tip:core/rcu] idr: Apply " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 12/21] security: apply lockdep-based checking " Paul E. McKenney
2010-02-25 10:12   ` [tip:core/rcu] security: Apply " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 13/21] rcu: documentation update for CONFIG_PROVE_RCU Paul E. McKenney
2010-02-25 10:12   ` [tip:core/rcu] rcu: Documentation " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 14/21] rcu: fix citation of Mathieu's dissertation Paul E. McKenney
2010-02-25 10:13   ` [tip:core/rcu] rcu: Fix " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 15/21] rcu: accelerate grace period if last non-dynticked CPU Paul E. McKenney
2010-02-25 10:13   ` [tip:core/rcu] rcu: Accelerate " tip-bot for Paul E. McKenney
2010-02-23  1:05 ` [PATCH tip/core/rcu 16/21] rcu: use canonical URL for Mathieu's dissertation Paul E. McKenney
2010-02-25 10:13   ` [tip:core/rcu] rcu: Use " tip-bot for Paul E. McKenney
2010-02-23  1:05 ` [PATCH tip/core/rcu 17/21] rcu: stop overflowing signed integers Paul E. McKenney
2010-02-25 10:14   ` [tip:core/rcu] rcu: Stop " tip-bot for Paul E. McKenney
2010-02-23  1:05 ` [PATCH tip/core/rcu 18/21] rcu: Convert to raw_spinlocks Paul E. McKenney
2010-02-25 10:14   ` [tip:core/rcu] " tip-bot for Paul E. McKenney
2010-02-23  1:05 ` [PATCH tip/core/rcu 19/21] rcu: fix deadlock in TREE_PREEMPT_RCU CPU stall detection Paul E. McKenney
2010-02-25 10:14   ` [tip:core/rcu] rcu: Fix " tip-bot for Paul E. McKenney
2010-02-23  1:05 ` [PATCH tip/core/rcu 20/21] rcu: fix rcutorture mod_timer argument to delay one jiffy Paul E. McKenney
2010-02-25 10:14   ` [tip:core/rcu] rcu: Fix " tip-bot for Paul E. McKenney
2010-02-23  1:05 ` [PATCH tip/core/rcu 21/21] rcu: add RCU_CPU_STALL_VERBOSE to dump detailed per-task information Paul E. McKenney
2010-02-25 10:15   ` [tip:core/rcu] rcu: Add " tip-bot for Paul E. McKenney
2010-02-23 12:59 ` [PATCH tip/core/rcu 0/21] v6 add lockdep-based diagnostics to rcu_dereference() Arnd Bergmann
2010-02-23 13:15   ` Mathieu Desnoyers
2010-02-23 14:35     ` Paul E. McKenney
2010-02-23 15:54     ` Arnd Bergmann
2010-02-23 16:16       ` Paul E. McKenney
2010-02-23 17:15         ` Arnd Bergmann
2010-02-23 18:01           ` Paul E. McKenney
2010-02-24 20:03             ` [PATCH 00/10] __rcu annotations, first draft Arnd Bergmann
2010-02-24 22:18               ` Paul E. McKenney
2010-02-25  8:37               ` Ingo Molnar
2010-02-24 20:03             ` [PATCH 01/10] rcu: define __rcu address space modifier for sparse Arnd Bergmann
2010-02-24 20:12               ` Mathieu Desnoyers
2010-02-24 20:22                 ` Arnd Bergmann
2010-02-24 20:03             ` [PATCH 02/10] rcu: annotated list rcu code Arnd Bergmann
2010-02-24 20:15               ` Mathieu Desnoyers
2010-02-24 20:32                 ` Arnd Bergmann [this message]
2010-02-24 20:03             ` [PATCH 03/10] cgroups: __rcu annotations Arnd Bergmann
2010-02-24 20:04             ` [PATCH 04/10] credentials: rcu annotation Arnd Bergmann
2010-02-24 20:04             ` [PATCH 05/10] perf_event: __rcu annotations Arnd Bergmann
2010-02-24 20:04             ` [PATCH 06/10] audit: " Arnd Bergmann
2010-02-24 20:04             ` [PATCH 07/10] module: " Arnd Bergmann
2010-02-24 20:13               ` Alexey Dobriyan
2010-02-24 20:26                 ` Arnd Bergmann
2010-02-24 22:17                   ` Paul E. McKenney
2010-02-24 23:07                     ` Arnd Bergmann
2010-02-24 23:59                       ` Paul E. McKenney
2010-02-25 17:06                         ` Paul E. McKenney
2010-02-25 18:10                           ` Arnd Bergmann
2010-02-25 20:05                             ` Paul E. McKenney
2010-02-26  2:12                               ` Paul E. McKenney
2010-02-24 20:04             ` [PATCH 08/10] pid: " Arnd Bergmann
2010-02-24 20:04             ` [PATCH 09/10] notifiers: " Arnd Bergmann
2010-02-24 20:04             ` [PATCH 10/10] scheduler: " Arnd Bergmann
2010-02-23 13:28   ` [PATCH tip/core/rcu 0/21] v6 add lockdep-based diagnostics to rcu_dereference() Paul E. McKenney
2010-02-25 10:00 ` Ingo Molnar
2010-02-25 10:01   ` Ingo Molnar
2010-02-25 12:04     ` Ingo Molnar
2010-02-25 18:18       ` Paul E. McKenney
2010-02-25 21:36         ` Paul E. McKenney
2010-02-25 21:22       ` Ingo Molnar

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