From: Arnd Bergmann <arnd@arndb.de>
To: paulmck@linux.vnet.ibm.com
Cc: Alexey Dobriyan <adobriyan@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.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 07/10] module: __rcu annotations
Date: Thu, 25 Feb 2010 19:10:34 +0100 [thread overview]
Message-ID: <201002251910.34938.arnd@arndb.de> (raw)
In-Reply-To: <20100225170653.GA5715@linux.vnet.ibm.com>
On Thursday 25 February 2010, Paul E. McKenney wrote:
> >
> > The nice thing about this is that we don't end up with the API explosion
> > for the RCU list primitives. However, it does require that a given
> > rcu_list_head have a single synchronization-design rule for all uses.
> > Of course, if there were multiple rules, one could construct a check
> > that was simply the union of all the rules, but that would miss some
> > types of errors.
What would it miss? E.g. having the module code check for
(mutex_is_locked(&module_lock) || rcu_read_lock_held) should
cover all cases as far as I can tell.
> > Of course, if this became a problem, there could be an argument to the
> > ->check function that the normal list_for_each_entry_rcu() defaults to
> > "no effect".
I've also been thinking about adding a list_for_each_entry_norcu()
macro that takes an rcu_list_head but then just performs a simple
list_for_each_entry().
> > Or is there a better way to handle this?
>
> One approach would be to use your original sparse-based approach, but
> use an rcu_deference_const(ptr,lockdep_condition) for cases when the
> value cannot change, for example, when the update-side lock is held.
> This should eliminate most of the false positives, in particular,
> eliminate the need for otherwise-useless rcu_read_lock()s -- and also
> for the compiler constraints in the normal rcu_dereference().
Right.
> Your pointer-to-function idea could be a really cool way to handle the
> tree algorithms that can be protected either by RCU or by locking.
> The tree nodes could have the pointer to check function, and the
> current rcu_dereference_raw() calls could be replaced by an invocation
> of rcu_dereference_check() that calls the check function. A check
> function for an RCU-protected tree would use "rcu_read_lock_held() ||
> lockdep_is_held(&update_side_lock)", while a lock-protected tree would
> just use "lockdep_is_held(&update_side_lock)".
I've postponed that problem for now, and updated my series to split
the rculist annotations from the basic __rcu pointer annotations,
as well as to apply on top of your patches in tip/core/rcu,
see http://git.kernel.org/?p=linux/kernel/git/arnd/playground.git;\
a=shortlog;h=refs/heads/rcu-annotate-tip.
Should we merge the simple annotations in this merge window and
then think about rculist and trees separately?
Arnd
next prev parent reply other threads:[~2010-02-25 18:12 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
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 [this message]
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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