From: Josh Triplett <josh@joshtriplett.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, Valdis.Kletnieks@vt.edu,
dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com,
fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org,
"Paul E. McKenney" <paul.mckenney@linaro.org>
Subject: Re: [PATCH tip/core/rcu 04/15] rcu: Permit RCU_NONIDLE() to be used from interrupt context
Date: Fri, 31 Aug 2012 11:00:52 -0700 [thread overview]
Message-ID: <20120831180052.GB4259@jtriplet-mobl1> (raw)
In-Reply-To: <1346352988-32444-4-git-send-email-paulmck@linux.vnet.ibm.com>
On Thu, Aug 30, 2012 at 11:56:17AM -0700, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paul.mckenney@linaro.org>
>
> There is a need to use RCU from interrupt context, but either before
> rcu_irq_enter() is called or after rcu_irq_exit() is called. If the
> interrupt occurs from idle, then lockdep-RCU will complain about such
> uses, as they appear to be illegal uses of RCU from the idle loop.
> In other environments, RCU_NONIDLE() could be used to properly protect
> the use of RCU, but RCU_NONIDLE() currently cannot be invoked except
> from process context.
>
> This commit therefore modifies RCU_NONIDLE() to permit its use more
> globally.
>
> Reported-by: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Something seems wrong about this. The addition of EXPORT_SYMBOL_GPL
suggests that such interrupt handlers might live in modules. In what
situation might a module interrupt handler get called from the idle
loop, before rcu_irq_enter or after rcu_irq_exit, and need to know that
when using RCU?
- Josh Triplett
> ---
> include/linux/rcupdate.h | 6 ++----
> kernel/rcutiny.c | 2 ++
> kernel/rcutree.c | 2 ++
> 3 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 115ead2..0fbbd52 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -210,14 +210,12 @@ extern void exit_rcu(void);
> * to nest RCU_NONIDLE() wrappers, but the nesting level is currently
> * quite limited. If deeper nesting is required, it will be necessary
> * to adjust DYNTICK_TASK_NESTING_VALUE accordingly.
> - *
> - * This macro may be used from process-level code only.
> */
> #define RCU_NONIDLE(a) \
> do { \
> - rcu_idle_exit(); \
> + rcu_irq_enter(); \
> do { a; } while (0); \
> - rcu_idle_enter(); \
> + rcu_irq_exit(); \
> } while (0)
>
> /*
> diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
> index e4163c5..2e073a2 100644
> --- a/kernel/rcutiny.c
> +++ b/kernel/rcutiny.c
> @@ -115,6 +115,7 @@ void rcu_irq_exit(void)
> rcu_idle_enter_common(newval);
> local_irq_restore(flags);
> }
> +EXPORT_SYMBOL_GPL(rcu_irq_exit);
>
> /* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */
> static void rcu_idle_exit_common(long long oldval)
> @@ -172,6 +173,7 @@ void rcu_irq_enter(void)
> rcu_idle_exit_common(oldval);
> local_irq_restore(flags);
> }
> +EXPORT_SYMBOL_GPL(rcu_irq_enter);
>
> #ifdef CONFIG_DEBUG_LOCK_ALLOC
>
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index f280e54..96b8aff 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -447,6 +447,7 @@ void rcu_irq_exit(void)
> rcu_idle_enter_common(rdtp, oldval);
> local_irq_restore(flags);
> }
> +EXPORT_SYMBOL_GPL(rcu_irq_exit);
>
> /*
> * rcu_idle_exit_common - inform RCU that current CPU is moving away from idle
> @@ -542,6 +543,7 @@ void rcu_irq_enter(void)
> rcu_idle_exit_common(rdtp, oldval);
> local_irq_restore(flags);
> }
> +EXPORT_SYMBOL_GPL(rcu_irq_enter);
>
> /**
> * rcu_nmi_enter - inform RCU of entry to NMI context
> --
> 1.7.8
>
next prev parent reply other threads:[~2012-08-31 18:01 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-30 18:56 [PATCH tip/core/rcu 0/15] Miscellaneous fixes Paul E. McKenney
2012-08-30 18:56 ` [PATCH tip/core/rcu 01/15] rcu: Add PROVE_RCU_DELAY to provoke difficult races Paul E. McKenney
2012-08-30 18:56 ` [PATCH tip/core/rcu 02/15] rcu: Pull TINY_RCU dyntick-idle tracing into non-idle region Paul E. McKenney
2012-08-31 16:53 ` Josh Triplett
2012-08-30 18:56 ` [PATCH tip/core/rcu 03/15] rcu: Properly initialize ->boost_tasks on CPU offline Paul E. McKenney
2012-08-31 17:56 ` Josh Triplett
2012-09-06 14:40 ` Peter Zijlstra
2012-09-06 20:58 ` Paul E. McKenney
2012-08-30 18:56 ` [PATCH tip/core/rcu 04/15] rcu: Permit RCU_NONIDLE() to be used from interrupt context Paul E. McKenney
2012-08-31 18:00 ` Josh Triplett [this message]
2012-09-04 22:33 ` Paul E. McKenney
2012-09-04 22:48 ` Josh Triplett
2012-09-04 22:51 ` Steven Rostedt
2012-09-04 23:08 ` Josh Triplett
2012-09-04 23:23 ` Steven Rostedt
2012-09-04 23:33 ` Josh Triplett
2012-09-04 23:43 ` Paul E. McKenney
2012-09-06 18:54 ` Josh Triplett
2012-09-06 19:54 ` Steven Rostedt
2012-09-07 6:09 ` Josh Triplett
2012-09-07 14:24 ` Paul E. McKenney
2012-09-07 14:47 ` Josh Triplett
2012-09-07 15:16 ` Steven Rostedt
2012-09-12 1:07 ` Paul E. McKenney
2012-09-12 14:13 ` Steven Rostedt
2012-09-12 15:03 ` Paul E. McKenney
2012-09-12 15:18 ` Steven Rostedt
2012-09-12 16:57 ` Paul E. McKenney
2012-09-04 23:46 ` Steven Rostedt
2012-09-05 0:42 ` Josh Triplett
2012-09-05 6:23 ` [PATCH] trace: Don't declare trace_*_rcuidle functions in modules Josh Triplett
2012-09-05 14:26 ` Mathieu Desnoyers
2012-09-05 16:36 ` Paul E. McKenney
2012-09-06 19:49 ` Steven Rostedt
2012-09-14 6:07 ` [tip:core/rcu] trace: Don' t " tip-bot for Josh Triplett
2012-09-04 23:14 ` [PATCH tip/core/rcu 04/15] rcu: Permit RCU_NONIDLE() to be used from interrupt context Paul E. McKenney
2012-08-30 18:56 ` [PATCH tip/core/rcu 05/15] rcu: Improve boost selection when moving tasks to root rcu_node Paul E. McKenney
2012-08-31 18:09 ` Josh Triplett
2012-08-30 18:56 ` [PATCH tip/core/rcu 06/15] rcu: Make offline-CPU checking allow for indefinite delays Paul E. McKenney
2012-08-31 18:12 ` Josh Triplett
2012-08-30 18:56 ` [PATCH tip/core/rcu 07/15] rcu: Fix obsolete rcu_initiate_boost() header comment Paul E. McKenney
2012-08-31 18:13 ` Josh Triplett
2012-08-30 18:56 ` [PATCH tip/core/rcu 08/15] rcu: Apply for_each_rcu_flavor() to increment_cpu_stall_ticks() Paul E. McKenney
2012-08-31 18:15 ` Josh Triplett
2012-09-04 22:44 ` Paul E. McKenney
2012-08-30 18:56 ` [PATCH tip/core/rcu 09/15] rcu: Avoid rcu_print_detail_task_stall_rnp() segfault Paul E. McKenney
2012-08-31 18:19 ` Josh Triplett
2012-09-04 22:46 ` Paul E. McKenney
2012-09-04 22:55 ` Josh Triplett
2012-08-30 18:56 ` [PATCH tip/core/rcu 10/15] rcu: Protect rcu_node accesses during CPU stall warnings Paul E. McKenney
2012-08-31 18:23 ` Josh Triplett
2012-09-04 22:51 ` Paul E. McKenney
2012-09-06 14:51 ` Peter Zijlstra
2012-09-06 21:01 ` Paul E. McKenney
2012-08-30 18:56 ` [PATCH tip/core/rcu 11/15] rcu: Avoid spurious RCU " Paul E. McKenney
2012-08-31 18:24 ` Josh Triplett
2012-09-06 14:56 ` Peter Zijlstra
2012-09-06 15:07 ` Steven Rostedt
2012-09-06 15:19 ` Peter Zijlstra
2012-09-06 21:03 ` Paul E. McKenney
2012-09-06 21:41 ` Steven Rostedt
2012-09-06 21:58 ` Paul E. McKenney
2012-09-06 22:05 ` Steven Rostedt
2012-09-06 22:22 ` Paul E. McKenney
2012-09-07 7:00 ` Peter Zijlstra
2012-09-07 14:42 ` Steven Rostedt
2012-08-30 18:56 ` [PATCH tip/core/rcu 12/15] rcu: Remove redundant memory barrier from __call_rcu() Paul E. McKenney
2012-08-31 18:30 ` Josh Triplett
2012-08-31 18:40 ` Josh Triplett
2012-08-30 18:56 ` [PATCH tip/core/rcu 13/15] rcu: Move TINY_PREEMPT_RCU away from raw_local_irq_save() Paul E. McKenney
2012-08-31 18:34 ` Josh Triplett
2012-09-04 23:03 ` Paul E. McKenney
2012-08-30 18:56 ` [PATCH tip/core/rcu 14/15] time: RCU permitted to stop idle entry via softirq Paul E. McKenney
2012-08-31 18:51 ` Josh Triplett
2012-09-06 15:12 ` Peter Zijlstra
2012-09-06 21:35 ` Paul E. McKenney
2012-09-06 21:57 ` Steven Rostedt
2012-09-06 22:11 ` Paul E. McKenney
2012-08-30 18:56 ` [PATCH tip/core/rcu 15/15] kmemleak: Replace list_for_each_continue_rcu with new interface Paul E. McKenney
2012-08-31 18:55 ` Josh Triplett
2012-09-04 23:41 ` Paul E. McKenney
2012-08-31 16:49 ` [PATCH tip/core/rcu 01/15] rcu: Add PROVE_RCU_DELAY to provoke difficult races Josh Triplett
2012-09-04 22:36 ` Paul E. McKenney
2012-09-06 14:38 ` Peter Zijlstra
2012-09-06 20:51 ` Paul E. McKenney
2012-09-07 6:54 ` Peter Zijlstra
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