Messages in this thread | | | Date | Fri, 31 Aug 2012 11:00:52 -0700 | From | Josh Triplett <> | Subject | Re: [PATCH tip/core/rcu 04/15] rcu: Permit RCU_NONIDLE() to be used from interrupt context |
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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 >
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